only _kill() when there's no servers *and* the event queue is empty

this is so that bitbot doesn't exit when you !reconnect but only have 1 server

src/IRCBot.py

@@ -273,7 +273,7 @@ class Bot(object):
 
     def _event_loop(self):
         while self.running or not self._event_queue.empty():
-            if not self.servers:
+            if not self.servers and self._event_queue.empty():
                 self._kill()
                 self.log.warn("No servers, exiting")
                 break