Merge "Guard potential null case in FullscreenTaskListener.releaseWindowDecor found in testing." into tm-qpr-dev am: 21688acee8

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19794348

Change-Id: Ic40a7e4647c0620462bcadbaf7aacc71e42158cd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

libs/WindowManager/Shell/src/com/android/wm/shell/fullscreen/FullscreenTaskListener.java

@@ -287,6 +287,9 @@ public class FullscreenTaskListener<T extends AutoCloseable>
     }
 
     private void releaseWindowDecor(T windowDecor) {
+        if (windowDecor == null) {
+            return;
+        }
         try {
             windowDecor.close();
         } catch (Exception e) {