issues when click child menu

[selvam920]

ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
At this point the state of the widget's element tree is no longer stable.
To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
#0 Element._debugCheckStateIsActiveForAncestorLookup.
package:flutter/…/widgets/framework.dart:4001
#1 Element._debugCheckStateIsActiveForAncestorLookup
package:flutter/…/widgets/framework.dart:4015
#2 Element.findAncestorStateOfType
package:flutter/…/widgets/framework.dart:4062

[bosskmk]

I can't tell what kind of error it is just by looking at your error.
Can you attach the minimum source code to reproduce the error?