Deallocate the pixbuf data when the AsbApp has been saved
Deallocate the pixbuf data when the AsbApp has been saved

This reduces the amount of memory used by a huge amount.

superm1/appstream-glib,mitya57/appstream-glib,ximion/appstream-glib,kalev/appstream-glib,superm1/appstream-glib,mitya57/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,ikeydoherty/appstream-glib,kalev/appstream-glib,ikeydoherty/appstream-glib,hughsie/appstream-glib