Suppress game input while debug menu is active

[schlangz]

I was tearing my eyes out why I'm getting sent to the race results when flipping the hardware rendering property in the debug menu.

roller.c function UpdateSDL() thats how I fixed it:

    debug_overlay_handle_event(s_pDebugOverlay, &e);
    if (!debug_overlay_visible(s_pDebugOverlay)) {
      InputHandleEvent(&e);
      frontend_mouse_handle_event(&e);
    }

[Zizin13]

You can make a PR for this as well