Fix TransitionManager.go() to allow null transitions

The doc'd behavior of go() is that a null transition is equivalent
to just switching to a scene with no transition. The actual behavior
was an NPE crash.

Issue #17342291 TransitionManager.go() with null Transition parameter throws NPE unlike documentation

Change-Id: I9416aa6e307f80eefc201ca3264fd64f8587ac2f

1 files changed, 7 insertions, 3 deletions

diff --git a/core/java/android/transition/TransitionManager.java b/core/java/android/transition/TransitionManager.java
index ce3cc2f..7bd6287 100644
--- a/core/java/android/transition/TransitionManager.java
+++ b/core/java/android/transition/TransitionManager.java
@@ -182,11 +182,15 @@ public class TransitionManager {
 
         final ViewGroup sceneRoot = scene.getSceneRoot();
 
-        Transition transitionClone = transition.clone();
-        transitionClone.setSceneRoot(sceneRoot);
+        Transition transitionClone = null;
+        if (transition != null) {
+            transitionClone = transition.clone();
+            transitionClone.setSceneRoot(sceneRoot);
+        }
 
         Scene oldScene = Scene.getCurrentScene(sceneRoot);
-        if (oldScene != null && oldScene.isCreatedFromLayoutResource()) {
+        if (oldScene != null && transitionClone != null &&
+                oldScene.isCreatedFromLayoutResource()) {
             transitionClone.setCanRemoveViews(true);
         }