core: Notify when an operation is performed over invalid operation_id
core: Notify when an operation is performed over invalid operation_id

It is actually done, but no message is actually shown to developer.

kyoushuu/grilo,grilofw/grilo,grilofw/grilo,MathieuDuponchelle/grilo,GNOME/grilo,jasuarez/grilo,MathieuDuponchelle/grilo,jasuarez/grilo,kyoushuu/grilo,MathieuDuponchelle/grilo,kyoushuu/grilo,grilofw/grilo,jasuarez/grilo,kyoushuu/grilo,GNOME/grilo