Getting this error on ios build ?

[BAssured]

flutter_clean_architecture-5.0.4/lib/src/view.dart:142:29: Error: Method 'addObserver' cannot be called on 'WidgetsBinding?' because it is potentially null.

'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Desktop/projects/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
WidgetsBinding.instance.addObserver(_controller);
^^^^^^^^^^^
Failed to package com.example.app.
Command PhaseScriptExecution failed with a nonzero exit code