core: Prevent crash in ImportResource
core: Prevent crash in ImportResource

Throw error when required input arguments are missing.

Tarnyko/rygel,GNOME/rygel,jku/rygel,luisbg/rygel,GNOME/rygel,Pelagicore/Media-Manager-Rygel-patched,jku/rygel,Pelagicore/Media-Manager-Rygel-patched,Tarnyko/rygel,Pelagicore/Media-Manager-Rygel-patched,GNOME/rygel