I am getting flex constant error

[5exceptions-megharaypuriya]

Flex Constant Erorr
I have just pub get the dependencies when I added code bottom navigation bar and then run afterwards it give me error which mention in below please find.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See the error

../../../../../.pub-cache/hosted/pub.dev/stylish_bottom_bar-1.0.3/lib/src/bottom_bar.dart:421:21: Error: Cannot invoke a non-'const' constructor where a const expression is expected.
Try using a constructor or factory that is 'const'.
? const Flex(
^^^^
Target kernel_snapshot failed: Exception

FAILURE: Build failed with an exception.

• Where:
  Script '/Applications/development/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 1151

• What went wrong:
  Execution failed for task ':app:compileFlutterBuildDebug'.

Process 'command '/Applications/development/flutter/bin/flutter'' finished with non-zero exit value 1