Issue 1:
I/flutter (16829): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (16829): The following assertion was thrown building AvailabilityDetail(dirty, state:
I/flutter (16829): AvailabilityDetailPageState#3c6d4):
I/flutter (16829): 'package:flutter/src/widgets/text.dart': Failed assertion: line 230 pos 15: 'data != null': is not
I/flutter (16829): true.
I/flutter (16829):
I/flutter (16829): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter (16829): more information in this error message to help you determine and fix the underlying cause.
I/flutter (16829): In either case, please report this assertion by filing a bug on GitHub:
I/flutter (16829): https://github.com/flutter/flutter/issues/new
I/flutter (16829):
I/flutter (16829): When the exception was thrown, this was the stack:
I/flutter (16829): #2 new Text (package:flutter/src/widgets/text.dart:230:15)
I/flutter (16829): #3 getAppBar (package:sipaper/CustomAppBar.dart:16:12)
I/flutter (16829): #4 AvailabilityDetailPageState.build (package:sipaper/pi_chart_detail_view.dart:122:15)
I/flutter (16829): #5 StatefulElement.build (package:flutter/src/widgets/framework.dart:3766:27)
I/flutter (16829): #6 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3678:15)
I/flutter (16829): #7 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #8 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #9 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #10 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #11 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #12 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #13 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #14 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #15 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #16 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #17 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #18 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #19 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #20 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #21 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #22 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #23 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #24 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #25 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #26 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #27 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #28 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #30 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #31 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #32 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #33 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #34 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #35 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #36 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #37 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #38 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #39 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #40 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #41 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #42 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #43 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #44 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #45 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #46 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #47 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #48 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #49 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #50 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #51 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #52 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #53 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #54 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #55 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #56 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #57 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #58 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #59 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #60 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #61 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #62 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #63 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #64 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #65 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #66 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #67 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #68 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #69 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #70 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #71 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #72 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #73 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #74 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #75 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #76 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #77 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #78 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #79 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4796:14)
I/flutter (16829): #80 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #81 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #82 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #83 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #84 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #85 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #86 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #87 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #88 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #89 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #90 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #91 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #92 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #93 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #94 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #95 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #96 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #97 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3658:5)
I/flutter (16829): #98 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3805:11)
I/flutter (16829): #99 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3653:5)
I/flutter (16829): #100 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2937:14)
I/flutter (16829): #101 Element.updateChild (package:flutter/src/widgets/framework.dart:2740:12)
I/flutter (16829): #102 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4579:32)
I/flutter (16829): #103 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4911:17)
I/flutter (16829): #104 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #105 _TheatreElement.update (package:flutter/src/widgets/overlay.dart:507:16)
I/flutter (16829): #106 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #107 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #108 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #109 StatefulElement.update (package:flutter/src/widgets/framework.dart:3835:5)
I/flutter (16829): #110 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #111 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #112 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #113 ProxyElement.update (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter (16829): #114 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #115 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4803:14)
I/flutter (16829): #116 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #117 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #118 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #119 StatefulElement.update (package:flutter/src/widgets/framework.dart:3835:5)
I/flutter (16829): #120 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #121 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4803:14)
I/flutter (16829): #122 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #123 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4803:14)
I/flutter (16829): #124 Element.updateChild (package:flutter/src/widgets/framework.dart:2729:15)
I/flutter (16829): #125 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3689:16)
I/flutter (16829): #126 Element.rebuild (package:flutter/src/widgets/framework.dart:3531:5)
I/flutter (16829): #127 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2273:33)
I/flutter (16829): #128 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:653:20)
I/flutter (16829): #129 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter (16829): #130 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (16829): #131 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (16829): #132 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter (16829): #133 _invoke (dart:ui/hooks.dart:128:13)
I/flutter (16829): #134 _drawFrame (dart:ui/hooks.dart:117:3)
I/flutter (16829): (elided 2 frames from class _AssertionError)

Issue 2:
'package:flutter/src/widgets/text.dart': Failed assertion: line 207 pos 15: 'data != null': is not
I/flutter (17269): true.
I/flutter (17269):
I/flutter (17269): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter (17269): more information in this error message to help you determine and fix the underlying cause.
I/flutter (17269): In either case, please report this assertion by filing a bug on GitHub:
I/flutter (17269): https://github.com/flutter/flutter/issues/new

If the text is null, then the assertion fails. This seems like something that can happen easily with new users.