Fix a regression of the commit 940c9998e5cfffd90fade8a7f39f29a426e20460 Unlike key event, mouse event will not be chained up to parent window by DefWindowProc Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/718>
Fix a regression of the commit 940c9998e5cfffd90fade8a7f39f29a426e20460 Unlike key event, mouse event will not be chained up to parent window by DefWindowProc Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/718>