Bug #28953 Using events in a replication let the slave crash.

Fixed where the slave code would try to update the Lex->sphead which is NULL on an "alter table" commands.

mysql-test/r/rpl_events.result

@@ -157,3 +157,9 @@ test	slave_terminate	SLAVESIDE_DISABLED	2
 DROP EVENT test.slave_terminate;
 "in the master"
 DROP TABLE t1;
+CREATE EVENT event1 ON SCHEDULE EVERY 1 YEAR
+DO BEGIN
+select * from t1;
+END;|
+ALTER EVENT event1 RENAME TO event2;
+DROP EVENT event2;

mysql-test/t/rpl_events.test

@@ -22,3 +22,26 @@ set binlog_format=statement;
 # Embedded server doesn't support binlogging
 --source include/rpl_events.inc
 
+#
+# Bug #28953  	Using events in a replication let the slave crash.
+#
+
+connection master;
+
+DELIMITER |;
+CREATE EVENT event1 ON SCHEDULE EVERY 1 YEAR
+DO BEGIN
+	select * from t1;
+END;|
+DELIMITER ;|
+
+ALTER EVENT event1 RENAME TO event2;
+
+sync_slave_with_master;
+
+connection master;
+
+DROP EVENT event2;
+
+sync_slave_with_master;
+

sql/sql_parse.cc

@@ -1567,7 +1567,7 @@ bool sp_process_definer(THD *thd)
     if (lex->definer == NULL)
       DBUG_RETURN(TRUE);
 
-    if (thd->slave_thread)
+    if (thd->slave_thread && lex->sphead)
       lex->sphead->m_chistics->suid= SP_IS_NOT_SUID;
   }
   else