Handle prefix being null when we've received a server notice (line_handler.py)

modules/line_handler.py

@@ -464,6 +464,7 @@ class Module(ModuleManager.BaseModule):
                 event["prefix"].hostmask == event["server"].name or
                 target == "*" or
                 (not event["prefix"].hostname and not event["server"].name)):
+            if event["prefix"]:
                 event["server"].name = event["prefix"].hostmask
 
             self._event(event, "server-notice", message=message,