ogl: fix single core crash

osx is missing, sorry but I'm too stupid for objective-c

Source/Plugins/Plugin_VideoOGL/Src/main.cpp

@@ -253,6 +253,7 @@ void VideoBackend::Video_Cleanup() {
 		OpcodeDecoder_Shutdown();
 		delete g_renderer;
 		g_renderer = NULL;
+		GLInterface->ClearCurrent();
 	}
 }