Prevent merging transitions if we don't handle it

- If we don't handle merging the transition, it will play sequentially
  after the current transition (see ag/26641113)

Bug: 330821548
Test: N/a
Change-Id: I7d35cc173d8ced8ba9b9df02dd8a571ca08e9de7

quickstep/src/com/android/quickstep/util/FadeOutRemoteTransition.kt

@@ -37,12 +37,7 @@ class FadeOutRemoteTransition : IRemoteTransition.Stub() {
         mergeTarget: IBinder,
         finishCB: IRemoteTransitionFinishedCallback
     ) {
-
-        try {
-            finishCB.onTransitionFinished(null, Transaction())
-        } catch (e: RemoteException) {
-            // Ignore
-        }
+        // Do not report finish if we don't know how to handle this transition.
     }
 
     override fun startAnimation(

quickstep/src/com/android/quickstep/util/SplitSelectStateController.java

@@ -772,7 +772,9 @@ public class SplitSelectStateController {
         @Override
         public void mergeAnimation(IBinder transition, TransitionInfo info,
                 SurfaceControl.Transaction t, IBinder mergeTarget,
-                IRemoteTransitionFinishedCallback finishedCallback) { }
+                IRemoteTransitionFinishedCallback finishedCallback) {
+            // Do not report finish if we don't know how to handle this transition.
+        }
 
         @Override
         public void onTransitionConsumed(IBinder transition, boolean aborted)