Finish keyguard exit transition directly when no app involved

When there's no app involved when the keyguard exit, finish the
transition directly by calling the onAnimationFinished().

Otherwise, the transition may be stalled for a long time and cause
incorrect system state.

Bug: 364930619
Flag: com.android.window.flags.ensure_keyguard_does_transition_starting
Test: FlickerTestsAppLaunch-OpenAppFromLockscreenViaIntentTest
Change-Id: Id57efa11bdfeeda4fb5314e0591cf34295a04bf8