save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType()

Save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
Found this error when navigating the page to another
Basically in the parent scaffold widget should implement key: with global state

First declare the global state 

  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

Then in the Scaffold widget passing the key to it

Like so

Scaffold(

        key: _scaffoldKey,

        appBar: AppBar(

          title: const Text('Boorkmark'),

        ),