Resource leak in media_discoverer.

backport of [4e9d2f92] and [d12f65f6]

src/control/media_discoverer.c

@@ -178,8 +178,9 @@ libvlc_media_discoverer_new_from_name( libvlc_instance_t * p_inst,
 
     if( !p_mdis->p_sd )
     {
-        free( p_mdis );
         libvlc_exception_raise( p_e, "Can't find the services_discovery module named '%s'", psz_name );
+        libvlc_media_list_release( p_mdis->p_mlist );
+        free( p_mdis );
         return NULL;
     }