session: do not unref() NULL connection
session: do not unref() NULL connection

 #3  0x00007ffff59cfb3b in g_object_unref (_object=0x0) at gobject.c:2916
 #4  0x00007ffff6ea9c20 in socket_client_connect_ready (source_object=0x87ced0,
     result=0x8a58f0, data=0x7fffe3fffa80) at spice-session.c:1606
 #5  0x00007ffff5ea1278 in g_task_return_now (task=0x8a58f0) at gtask.c:1102

freedesktop-unofficial-mirror/spice__spice-gtk,flexVDI/spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,mathslinux/spice-gtk,fgouget/spice-gtk,elmarco/spice-gtk,Fantu/spice-gtk,mathslinux/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,Fantu/spice-gtk,elmarco/spice-gtk,fgouget/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,Fantu/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,flexVDI/spice-gtk,mathslinux/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,elmarco/spice-gtk,mathslinux/spice-gtk