while debugging https://github.com/flutter/flutter/issues/123882 found out that below lines were untested. although they'll change due to the issue above, but the tests will remain.

https://github.com/flutter/flutter/blob/e0045d04f7057d91b1701a444f75f2f0458c1d1a/packages/flutter/lib/src/material/scaffold.dart#L3169-L3180