Fix a stupid mistake during Definitions construction.
FIx NPE caused when Property Sheet is closed and reopened.
Fixed some more glaring bugs causing NPEs
Fixed a bug in ModelEnablements for extension attributes
New value for extension attributes can not be null - use default value.
Merge remote-tracking branch 'upstream/master'
tycho version changed
Merge branch 'master' of https://github.com/bennixview/bpmn2-modeler