tmdb: Fix warning in g_object_ref() assignment
tmdb: Fix warning in g_object_ref() assignment

grilo-plugins/src/tmdb/grl-tmdb.c: In function ‘grl_tmdb_source_resolve’:
grilo-plugins/src/tmdb/grl-tmdb.c:1346:17: warning: assignment to ‘GrlTmdbSource *’ {aka ‘struct _GrlTmdbSource *’} from incompatible pointer type ‘GrlSource *’ {aka ‘struct _GrlSource *’} [-Wincompatible-pointer-types]
   closure->self = g_object_ref (source);
                 ^

MikePetullo/grilo-plugins,GNOME/grilo-plugins,MikePetullo/grilo-plugins,jasuarez/grilo-plugins,grilofw/grilo-plugins,grilofw/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins,GNOME/grilo-plugins