GanttCalendarPlugin: avoid `KeyError: 'custom'` in `/ticketgantt` page

git-svn-id: http://svn.sourceforge.jp/svnroot/shibuya-trac/plugins/ganttcalendarplugin/trunk@856 456a77e7-5939-0410-b211-84f85430c667
GanttCalendarPlugin: fixed wrong label in table of the gantt view


git-svn-id: http://svn.sourceforge.jp/svnroot/shibuya-trac/plugins/ganttcalendarplugin/trunk@857 456a77e7-5939-0410-b211-84f85430c667
GanttCalendarPlugin: fixed an `TypeError` while comparing `due_assign` and `due_close` values (closes #34514)


git-svn-id: http://svn.sourceforge.jp/svnroot/shibuya-trac/plugins/ganttcalendarplugin/trunk@858 456a77e7-5939-0410-b211-84f85430c667
GanttCalendarPlugin: bumped up the version to 0.6.4


git-svn-id: http://svn.sourceforge.jp/svnroot/shibuya-trac/plugins/ganttcalendarplugin/trunk@859 456a77e7-5939-0410-b211-84f85430c667