Fix FloatingWidgetView post-animation fallback background handling am: e41034034f

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14440781

Change-Id: I56131e0b57e71de16f9b83525acf5e30f38ec221
diff --git a/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java b/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
index f74aa55..9ea2369 100644
--- a/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
+++ b/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
@@ -100,8 +100,8 @@
     /** Restores the drawables to the source view. */
     void finish() {
         if (isUninitialized()) return;
-        mSourceView.setForeground(mOriginalForeground);
-        mSourceView.setBackground(mOriginalBackground);
+        if (mOriginalForeground != null) mSourceView.setForeground(mOriginalForeground);
+        if (mOriginalBackground != null) mSourceView.setBackground(mOriginalBackground);
     }
 
     void recycle() {