gst_registry_find_plugin does not detect libav plugins created from FFMpeg
gst-libav plugins such as avdec_aac are not detected by a call to gst_registry_find_plugin(), even when gst-inspect-1.0 sees them
This is an issue because some libav plugins can be absent if an incomplete version of ffmpeg has been shipped by the distribution (for patent reasons, with a full version available elsewhere (e.g. Red Hat, rpmfusion)). If it is absent, gstreamer segfaults when the missing plugin is invoked in a pipeline.
(I am looking for a test for whether avdec_aac is available or not, to have a more graceful termination with an informative message if it isn't. gst_registry_find works for this for standard gstreamer plugins)