gdbusconnection: Add missing (nullable) to get_peer_credentials()
gdbusconnection: Add missing (nullable) to get_peer_credentials()

Since Colin mentioned it on gir-devel-list.

endlessm/glib,Distrotech/glib,cention-sany/glib,mzabaluev/glib,cention-sany/glib,ieei/glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,mzabaluev/glib,johne53/MB3Glib,cention-sany/glib,johne53/MB3Glib,mzabaluev/glib,Distrotech/glib,cention-sany/glib,johne53/MB3Glib,endlessm/glib,Distrotech/glib,MathieuDuponchelle/glib,ieei/glib,johne53/MB3Glib,mzabaluev/glib,mzabaluev/glib,ieei/glib,cention-sany/glib,ieei/glib,MathieuDuponchelle/glib,ieei/glib,endlessm/glib,MathieuDuponchelle/glib,Distrotech/glib,MathieuDuponchelle/glib,johne53/MB3Glib,Distrotech/glib,endlessm/glib