Fix NPEs in blocking code

Oops; actually check if we're online before snagging the XMPP connection

@iNPUTmice: I wasn't sure if the Account status had a contract such that it would be oflfine (or not online, anyways) if the `XmppConnection` was `null`, so I just checked for both to prevent any race conditions; if this isn't necessary, please advise and I'll change it to just check if the account status is `ONLINE`.

**EDIT:** I can't type apparently.