vaapidecode: Fix videocodec state memory leak
vaapidecode: Fix videocodec state memory leak

When state is not NULL and either width/height of video info is 0, then state leaks

https://bugzilla.gnome.org/show_bug.cgi?id=762173

01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi