Do not exit fullscreen if it was autoentered (#3273)

Author: keianhzo

app/src/common/shared/org/mozilla/vrbrowser/ui/widgets/NavigationBarWidget.java

@@ -160,7 +160,8 @@ private void initialize(@NonNull Context aContext) {
         };
         mVRVideoBackHandler = () -> {
             exitVRVideo();
-            if (mAttachedWindow != null) {
+            if (mAttachedWindow != null &&
+                    mViewModel.getAutoEnteredVRVideo().getValue().get()) {
                 mAttachedWindow.setIsFullScreen(false);
             }
         };