NoSuchMethodError after update to 0.5.0 #71

I'm getting following error after update to 0.5.0 version

I/flutter (21118): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (21118): The following NoSuchMethodError was thrown building Slidable(dirty, dependencies:
I/flutter (21118): [_ScrollableScope], state: SlidableState#1c8cb(tickers: tracking 1 ticker)):
I/flutter (21118): The method '[]' was called on null.
I/flutter (21118): Receiver: null
I/flutter (21118): Tried calling: [](Instance of 'SlideActionType')
I/flutter (21118):
I/flutter (21118): When the exception was thrown, this was the stack:
I/flutter (21118): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
I/flutter (21118): #1 SlidableState._dismissThreshold
package:flutter_slidable/…/widgets/slidable.dart:562
I/flutter (21118): #2 SlidableState.build
package:flutter_slidable/…/widgets/slidable.dart:897
I/flutter (21118): #3 StatefulElement.build
package:flutter/…/widgets/framework.dart:3825
I/flutter (21118): #4 ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:3739

widget.dismissal is null in _dismissThreshold

Adding some dummy check for null value in dismissal solves error (no idea why ?? operator is not working when ?. returns null...)