Got Assertion Error when scrolling the Upper layer of bottom sheet

[mcrovero]

Got Assertion Error when scrolling the Upper layer of bottom sheet

[CristianDRM]

I'm getting this error too

[DK15]

This PR fixes above issue.

[srcho8]

i have similar problem

════════ Exception caught by gesture ═════════
══════════════════════════════════
The following _CastError was thrown while handling a gesture:
Null check operator used on a null value

When the exception was thrown, this was the stack
#0 RubberAnimationController.stop
package:rubber/src/animation_controller.dart:500
#1 RubberAnimationController.value=
package:rubber/src/animation_controller.dart:254
#2 RubberBottomSheetState._onVerticalDragUpdate
package:rubber/src/bottom_sheet.dart:261
#3 DragGestureRecognizer._checkUpdate.
package:flutter/…/gestures/monodrag.dart:436
#4 GestureRecognizer.invokeCallback
package:flutter/…/gestures/recognizer.dart:182
...
Handler: "onUpdate"
Recognizer: VerticalDragGestureRecognizer#22e78
debugOwner: GestureDetector
start behavior: start
════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by gesture ═══════════════════════════════════════════
Null check operator used on a null value
════════════════════════════════════════════════════════════════════════════════