[vm] Fix a bug in the field exactness tracking state machine.
[vm] Fix a bug in the field exactness tracking state machine.

We were returning without initializing the state of the static
type exactness.

Change-Id: I447597cbe383470297a7f660addb60d0031cabba
Reviewed-on: https://dart-review.googlesource.com/70661
Reviewed-by: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>
Commit-Queue: Vyacheslav Egorov <72c81f38df725d8f1832acb9b5bb99563fc2f1b9@google.com>

dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk