Fixed sip_publish_presence to ignore error for already stopped reactor

Ignore-this: fc77329c0eb3921d16287e4ea71d480b

darcs-hash:20090408135233-1e3d8-c52df610b172df62a3b1fbd6616ef7bcf54ecd71
Fixed sip_subscribe_presence to ignore error for already stopped reactor

Ignore-this: e8b726bc056e94ea3b39883e1065d70f

darcs-hash:20090408135354-1e3d8-e5cf5f43ec3d5a595eb7b10ed75e7d4709bc9d31