There are about 370 failures in the framework unit tests when enabling sound null safety, probably drastically fewer unique failures. The PR is #68536

The failures are: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket.appspot.com/8865951167182274320/+/steps/download_dependencies/0/stdout?format=raw

One fix is: flutter/engine#21983