Error: Property 'count' cannot be accessed on 'JSValuePointer?' because it is potentially null.

[Gursewak-Uppal]

I have following error after migrate to null safety .

lib/js/js_engine.dart:71:32: Error: Property 'count' cannot be accessed on 'JSValuePointer?' because it is potentially null.
 - 'JSValuePointer' is from 'package:myApp/js/js_core_mock.dart' ('lib/js/js_core_mock.dart').
Try accessing using ?. instead.
      if (jsContext!.exception.count > 0) {
                               ^^^^^
lib/js/js_engine.dart:71:38: Error: Operator '>' cannot be called on 'int?' because it is potentially null.
      if (jsContext!.exception.count > 0) {
                                     ^
lib/js/js_engine.dart:72:50: Error: Property 'count' cannot be accessed on 'JSValuePointer?' because it is potentially null.
 - 'JSValuePointer' is from 'package:myApp/js/js_core_mock.dart' ('lib/js/js_core_mock.dart').
Try accessing using ?. instead.
        for (int i = 0; i < jsContext!.exception.count; i++)