Update AsyncTcpDispatcher.cs

1.Fix:
Somehow the SocketAsyncEventArgs were null for me sometime, so I checked if it is null...

2.Fix:
If trying to get the permissionlist it took from 90 to 120 Seconds (on localhost) to get it.
The problem was the regex checking every time the buffer was full.
Now I check if the statusline could be reached before trying to get it with regex, which increases the performance to a few seconds...