i am compiling my dart code for fllutter application ,whenever i try to compiled it i got these error related tp dart:ui

Question

i have fork a repo from git hub and try to run it by changing the keys to my own firebase project. but i keep getting error of dart:ui,i have already check pubspec.ymal file,but output is same.

PS C:\project\nssapp\lib>  cd "c:\project\nssapp\lib"
PS C:\project\nssapp\lib>  dart "c:\project\nssapp\lib\main.dart"
/C:/Users/Lenovo/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/emoji_picker_flutter-1.5.0/lib/src/skin_tone_overlay.dart:72:15: Warning: Operand of null-aware operation '?.' has type 'OverlayState' which excludes null.
 - 'OverlayState' is from 'package:flutter/src/widgets/overlay.dart' ('/C:/flutter/packages/flutter/lib/src/widgets/overlay.dart').
      Overlay.of(context)?.insert(_overlay!);
              ^
/C:/Users/Lenovo/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/google_fonts-3.0.1/lib/google_fonts.dart:7:8: Error: Not found: 'dart:ui'
import 'dart:ui' as ui;
       ^
/C:/flutter/packages/flutter/lib/src/material/animated_icons.dart:9:8: Error: Not found: 'dart:ui'
import 'dart:ui' as ui show Canvas, Paint, Path;
       ^
/C:/flutter/packages/flutter/lib/src/material/animated_icons.dart:10:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/app.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' as ui;
       ^
/C:/flutter/packages/flutter/lib/src/material/app_bar_theme.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/arc.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/banner_theme.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/bottom_app_bar_theme.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart:5:8: Error: Not found: 'dart:ui'      
import 'dart:ui' show lerpDouble;
       ^
/C:/flutter/packages/flutter/lib/src/material/bottom_sheet.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;