MDEV-23327: followup

fix an error with locked taböes

Author: sanja-byelkin

sql/sql_udf.cc

@@ -654,6 +654,12 @@ enum drop_udf_result mysql_drop_function(THD *thd, const LEX_STRING *udf_name)
  udf_func *udf;
  DBUG_ENTER("mysql_drop_function");
 
+ if (thd->locked_tables_mode)
+ {
+ my_error(ER_LOCK_OR_ACTIVE_TRANSACTION, MYF(0));
+ DBUG_RETURN(UDF_DEL_RESULT_ERROR);
+ }
+
  if (!(table= open_udf_func_table(thd)))
  DBUG_RETURN(UDF_DEL_RESULT_ERROR);