Fixed NullPointerException if there's no singleton

android-project/app/src/main/java/org/libsdl/app/SDLActivity.java

@@ -520,8 +520,10 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
     /* The native thread has finished */
     public static void handleNativeExit() {
         SDLActivity.mSDLThread = null;
+        if (mSingleton != null) {
             mSingleton.finish();
         }
+    }
 
 
     // Messages from the SDLMain thread