_GZXDropDownHeaderState setsState(() {}) line 64 error

[josephchenghmlet]

As title stated.

══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
I/flutter (19929): The following assertion was thrown while dispatching notifications for GZXDropdownMenuController:
I/flutter (19929): setState() called after dispose(): _GZXDropDownHeaderState#bfc38(lifecycle state: defunct, not
I/flutter (19929): mounted)
I/flutter (19929): This error happens if you call setState() on a State object for a widget that no longer appears in
I/flutter (19929): the widget tree (e.g., whose parent widget no longer includes the widget in its build). This error
I/flutter (19929): can occur when code calls setState() from a timer or an animation callback.
I/flutter (19929): The preferred solution is to cancel the timer or stop listening to the animation in the dispose()
I/flutter (19929): callback. Another solution is to check the "mounted" property of this object before calling
I/flutter (19929): setState() to ensure the object is still in the tree.
I/flutter (19929): This error might indicate a memory leak if setState() is being called because another object is
I/flutter (19929): retaining a reference to this State object after it has been removed from the tree. To avoid memory
I/flutter (19929): leaks, consider breaking the reference to this object during dispose().
I/flutter (19929): 
I/flutter (19929): When the exception was thrown, this was the stack:
I/flutter (19929): #0      State.setState.<anonymous closure> (package:flutter/src/widgets/framework.dart:1105:9)
I/flutter (19929): #1      State.setState (package:flutter/src/widgets/framework.dart:1140:6)
I/flutter (19929): #2      _GZXDropDownHeaderState._onController (package:gzx_dropdown_menu/src/gzx_dropdown_header.dart:64:5)
I/flutter (19929): #3      ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:206:21)
I/flutter (19929): #4      GZXDropdownMenuController.show (package:gzx_dropdown_menu/src/gzx_dropdown_menu_controller.dart:13:5)
I/flutter (19929): #5      _GZXDropDownHeaderState._menu.<anonymous closure> (package:gzx_dropdown_menu/src/gzx_dropdown_header.dart:124:29)
I/flutter (19929): #6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
I/flutter (19929): #7      TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:365:11)
I/flutter (19929): #8      TapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:312:7)
I/flutter (19929): #9      GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:156:27)
I/flutter (19929): #10     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:222:20)
I/flutter (19929): #11     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22)
I/flutter (19929): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
I/flutter (19929): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
I/flutter (19929): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
I/flutter (19929): #18     _invoke1 (dart:ui/hooks.dart:250:10)
I/flutter (19929): #19     _dispatchPointerDataPacket (dart:ui/hooks.dart:159:5)
I/flutter (19929): (elided 3 frames from package dart:async)
I/flutter (19929): 
I/flutter (19929): The GZXDropdownMenuController sending notification was:
I/flutter (19929):   Instance of 'GZXDropdownMenuController'
I/flutter (19929): ════════════════════════════════════════════════════════════════════════════════════════════════════

Will submit a new pull request soon.

[GanZhiXiong]

fix, merged request

#7 (comment)