Bugfix: fixing an edge case introduced by previous bugfix

lib/MySQL_Thread.cpp

@@ -1166,7 +1166,12 @@ void MySQL_Thread::run() {
 			sess->status=PINGING_SERVER;
 			myds->DSS=STATE_MARIADB_PING;
 			register_session_connection_handler(sess,true);
-			sess->handler();
+			int rc=sess->handler();
+			if (rc==-1) {
+				unsigned int sess_idx=mysql_sessions->len-1;
+				unregister_session(sess_idx);
+				delete sess;
+			}
 //			myds->myconn->async_ping(0);
 //			myds->myconn->async_state_machine=ASYNC_PING_START;
 //			myds->myconn->handler(0);