Don't crash when using 'appstream-util show-search-tokens'
Don't crash when using 'appstream-util show-search-tokens'

The private as_app_get_search_tokens() method needs to be AsRefString aware.

ximion/appstream-glib,hughsie/appstream-glib,ximion/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,hughsie/appstream-glib