Error when return OutlinedButton inside of the Mutation Widget

[sumchans]

I had the below widget working perfectly fine when I had the OutlinedButton.icon widget in place of the CreateUserMutation widget.

Widget build(BuildContext context) {
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: [
        Container(
          child: Column(
            children: [
              ListTile(
                leading: const Icon(
                  Icons.photo_library_rounded,
                  size: 35,
                  color: Colors.orange,
                ),
                title: const Text('Take a picture'),
                onTap: () {}
              ),
              CreateUserMutation(widget.user, widget.switchScreenFn),
            ],
          ),
        ),
      ],
    );
  }

Then I thought of cleaning the code a bit and moved the OutlinedButton.icon as below -

class CreateUserMutation extends StatelessWidget {
  const CreateUserMutation(this.user, {Key? key})
      : super(key: key);

  final User user;

  @override
  Widget build(BuildContext context) {
    return Mutation(
      options: MutationOptions(
        document: gql(graphql_string.createUserMutation),
        fetchPolicy: FetchPolicy.cacheAndNetwork,
        onCompleted: (data) {},
      ),
      builder: (runMutation, result) {
        return OutlinedButton.icon(
          icon: const Icon(Icons.arrow_right_alt),
           style: OutlinedButton.styleFrom(foregroundColor: Colors.black),
          label: const Text('Submit'),
          onPressed: () async {
            runMutation(
              {
                'id': const Uuid().v4(),
                'userPhoneNumber': user.phoneNumber,
                'userDisplayName': user.displayName,
              },
            );
          },
        );
      },
    );
  }
}

All of a sudden I get this error pointing to a location in the package. I am not able to figure out the root cause so far.

======== Exception caught by widgets library =======================================================
The following assertion was thrown building Mutation<Object?>(dirty):
'package:graphql_flutter/src/widgets/graphql_provider.dart': Failed assertion: line 58 pos 12: 'provider != null': is not true.

Here is the function it is pointing to in the package -

  factory _InheritedGraphQLProvider.of(BuildContext context) {
    final provider =
        context.dependOnInheritedWidgetOfExactType<_InheritedGraphQLProvider>();
    assert(provider != null);
    return provider!;
  }