body_might_complete_normally_nullable

This function has a nullable return type of '{0}', but ends without returning a value.

The analyzer produces this diagnostic when a method or function can implicitly return null by falling off the end. While this is valid Dart code, it's better for the return of null to be explicit.

The following code produces this diagnostic because the function f implicitly returns null:

String? f() {}

If the return of null is intentional, then make it explicit:

String? f() {
  return null;
}

If the function should return a non-null value along that path, then add the missing return statement:

String? f() {
  return '';
}