x264enc: remove useless and semantically (though not practically) wrong code
x264enc: remove useless and semantically (though not practically) wrong code

The object will be freed, so it's pointless to set the pointers
to NULL anyway.

fluendo/gst-plugins-ugly,fluendo/gst-plugins-ugly,matsu/gst-plugins-ugly,matsu/gst-plugins-ugly,matsu/gst-plugins-ugly,matsu/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-ugly,fluendo/gst-plugins-ugly