Do not change the leash after completion

Video: http://recall/-/aaaaaabFQoRHlzixHdtY/hDfsnKtrY7i5vJ41crnLhf
Bug: 284738852
Test: manually, follow the reproduce step, see also video
Change-Id: Iad166c1fb7b5db8c6bcd3abf0f3a0189747037da

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTransition.java

@@ -308,8 +308,9 @@ public class PipTransition extends PipTransitionController {
     @Override
     public void end() {
         Animator animator = mPipAnimationController.getCurrentAnimator();
-        if (animator == null) return;
-        animator.end();
+        if (animator != null && animator.isRunning()) {
+            animator.end();
+        }
     }
 
     @Override