libs: dmabuf: init the GST_CAT_DEFAULT in class define
To avoid gst_debug_log_valist: assertion 'category != NULL' failed
if we do not call gst_dmabuf_allocator_new
Edited by Nicolas Dufresne
To avoid gst_debug_log_valist: assertion 'category != NULL' failed
if we do not call gst_dmabuf_allocator_new