I got this exception ?

[radha1990kumari]

I don't what action leads to this :

The following _CastError was thrown while dispatching a pointer event:
Null check operator used on a null value

When the exception was thrown, this was the stack: 
#0      _SleekCircularSliderState._onPanDown (package:sleek_circular_slider/src/circular_slider.dart:285:58)
#1      _CustomPanGestureRecognizer.addPointer (package:sleek_circular_slider/src/custom_gesture_recognizer.dart:16:18)
#2      RawGestureDetectorState._handlePointerDown (package:flutter/src/widgets/gesture_detector.dart:1205:18)
#3      RenderPointerListener.handleEvent (package:flutter/src/rendering/proxy_box.dart:2829:29)
#4      GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:419:22)
...
Event: PointerDownEvent#4ef6d(position: Offset(233.0, 349.6))
  position: Offset(233.0, 349.6)
Target: RenderPointerListener#a3f84 relayoutBoundary=up9
  parentData: <none> (can use size)
  constraints: BoxConstraints(unconstrained)
  size: Size(150.0, 150.0)
  behavior: deferToChild
  listeners: down
====================================================================================================