Attempt to fix Emu.Quit()

There was some kind of "initialization order fiasco" of g_fxo.
Not only should it be used after main, but also destroyed before exit.

rpcs3/Emu/System.cpp

@@ -1971,6 +1971,9 @@ bool Emulator::Quit(bool force_quit)
 	m_force_boot = false;
 	Emu.Stop();
 
+	// Deinitialize object manager to prevent any hanging objects at program exit
+	*g_fxo = {};
+
 	return GetCallbacks().exit(force_quit);
 }