trivial: Fix applications doing Icon=/usr/share/pixmaps/app.png
trivial: Fix applications doing Icon=/usr/share/pixmaps/app.png

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