`Wrap with unawaited` false-negative for nullable futures

[FMorschel]

Repro:

class A {
  Future<void> m() async {}
}

void foo(A? a) {
  a?.m();
  if (a != null) {
    a.m();
  }
  a!.m();
}

For all cases above, the first (a?.m()) doesn't show Wrap with unawaited, but it does accept Future<void>?.

This happens no matter if foo is async or not, so the problem is with the quick-fix.