Fixed bug#19225: unchecked error results in server crash

In multi-table delete a table for delete can't be used for selecting in
subselects. Appropriate error was raised but wasn't checked which leads to a
crash at the execution phase.

The mysql_execute_command() now checks for errors before executing select
for multi-delete.

mysql-test/r/multi_update.result

@@ -475,3 +475,8 @@ aclid bigint, index idx_acl(aclid)
 insert into t2 values(1,null);
 delete t2, t1 from t2 left join t1 on (t2.aclid=t1.aclid) where t2.refid='1';
 drop table t1, t2;
+create table t1(a int);
+create table t2(a int);
+delete from t1,t2 using t1,t2 where t1.a=(select a from t1);
+ERROR HY000: You can't specify target table 't1' for update in FROM clause
+drop table t1, t2;

mysql-test/t/multi_update.test

@@ -448,4 +448,12 @@ insert into t2 values(1,null);
 delete t2, t1 from t2 left join t1 on (t2.aclid=t1.aclid) where t2.refid='1';
 drop table t1, t2;
 
+#
+# Bug#19225: unchecked error leads to server crash
+#
+create table t1(a int);
+create table t2(a int);
+--error 1093
+delete from t1,t2 using t1,t2 where t1.a=(select a from t1);
+drop table t1, t2;
 # End of 4.1 tests

sql/sql_parse.cc

@@ -3047,8 +3047,8 @@ mysql_execute_command(THD *thd)
       }
     }
 
-    if (!thd->is_fatal_error && (result= new multi_delete(thd,aux_tables,
-							  table_count)))
+    if (!res && !thd->is_fatal_error &&
+        (result= new multi_delete(thd,aux_tables, table_count)))
     {
       res= mysql_select(thd, &select_lex->ref_pointer_array,
 			select_lex->get_table_list(),