abort rid_brute on invalid connection after failed login

Author: azoxlpf

nxc/protocols/mssql.py

@@ -423,6 +423,9 @@ def handle_mssql_reply(self):
 
     def rid_brute(self, max_rid=None):
         entries = []
+        if self.conn.lastError:
+            self.logger.fail(f"Cannot perform RID bruteforce due to invalid connection: {self.conn.lastError}")
+            return entries
         if not max_rid:
             max_rid = int(self.args.rid_brute)