fix(mge/mm_handler): fix unused var ins

GitOrigin-RevId: 199d084e8f

python_module/src/cpp/mm_handler.cpp

@@ -222,6 +222,7 @@ public:
         server->run();
         auto ins = m_addr2server.emplace(
                 full_srv_addr, ServerInfo{std::move(server)});
+        mgb_assert(ins.second);
 
         return port;
     }