Error: google_fonts was unable to load font NunitoSans-Regular

How to fix? Thanks

```
I/flutter ( 8217): Error: google_fonts was unable to load font NunitoSans-Regular because the following exception occurred:
I/flutter ( 8217): Exception: GoogleFonts.config.allowRuntimeFetching is false but font NunitoSans-Regular was not found in the application assets. Ensure NunitoSans-Regular.ttf exists in a folder that is included in your pubspec's assets.
I/flutter ( 8217): See https://docs.flutter.dev/development/data-and-backend/networking#platform-notes.
I/flutter ( 8217): If troubleshooting doesn't solve the problem, please file an issue at https://github.com/material-foundation/flutter-packages/issues/new/choose.
E/flutter ( 8217): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Exception: GoogleFonts.config.allowRuntimeFetching is false but font NunitoSans-Regular was not found in the application assets. Ensure NunitoSans-Regular.ttf exists in a folder that is included in your pubspec's assets.
E/flutter ( 8217): #0 loadFontIfNecessary (package:google_fonts/src/google_fonts_base.dart:177)
E/flutter ( 8217):
```