Having problem inside the layout file

[Bengate-Technologies]

lib/layout.dart:17:29: Error: Required named parameter 'mediumScreen' must be provided.
body: ResponsiveWidget(largeScreen:LargeScreen(), smallScreen:SmallScreen(),),
^
lib/helpers/responsiveness.dart:14:9: Context: Found this candidate, but the arguments don't match.
const ResponsiveWidget(
^^^^^^^^^^^^^^^^
lib/helpers/responsiveness.dart:43:16: Warning: Operand of null-aware operation '??' has type
'Widget' which excludes null.

• 'Widget' is from 'package:flutter/src/widgets/framework.dart'
  ('/C:/src/flutter/packages/flutter/lib/src/widgets/framework.dart').
  return mediumScreen ?? largeScreen;
  ^
  lib/helpers/responsiveness.dart:46:16: Warning: Operand of null-aware operation '??' has type
  'Widget' which excludes null.
• 'Widget' is from 'package:flutter/src/widgets/framework.dart'
  ('/C:/src/flutter/packages/flutter/lib/src/widgets/framework.dart').
  return smallScreen ?? largeScreen;