Android: Keep the local copy of the mSurface

onCreateView might not be called after resuming the emulatoin wich will
leed the game to stuck in the middle since mRunWhenSurfaceIsValid will be
true but surfaceChanged will never be called in this case.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/EmulationFragment.java

@@ -306,7 +306,6 @@ public final class EmulationFragment extends Fragment implements SurfaceHolder.C
 				Log.debug("[EmulationFragment] Pausing emulation.");
 
 				// Release the surface before pausing, since emulation has to be running for that.
-				mSurface = null;
 				NativeLibrary.SurfaceDestroyed();
 				NativeLibrary.PauseEmulation();
 			}