Created attachment 296637 [details] [review]
lua-factory: Fix may_resolve with NULL media

grl_lua_factory_source_may_resolve might be called with media being NULL (via expand_operation_keys in grl-source.c for example). Currently this case is not handled properly and may_resolve calls grl_data_has_key which results in a critical warning because media is NULL. This is one of the sources of some of the critical warnings when running gnome-music.

I'm attaching a patch that handles this case by adding all required keys of the source to missing_keys since that is what seems to be what expand_operation_keys expects and what some other plugins (tmdb) seem to do as well. Some other plugins (metadata) and the example in the documentation however seem to indicate that simply returning FALSE would be enough.