fix bug when call wl_surface_set_input_region to set input region to Region(0, 0, 0, 0)

wayland window set the region to receive input events through wl_surface_set_input_region. Fix a bug when set Region(0, 0, 0, 0) will be return ture in acceptsInput according to Region(0, 0, 0, 0) the same as region.isEmpty. For example setting input region to Region(0, 0, 0, 0) to skip recorder window to receive input events. As recorder window is higher than desktop/file-manager and we want desktop/file-manager can receive input events as usual during recording.