Fix for bug#18224 VIEW on information_schema crashes the server

  additional check for subselect

mysql-test/r/information_schema.result

@@ -281,6 +281,13 @@ sub1	sub1
 select count(*) from information_schema.ROUTINES;
 count(*)
 2
+create view v1 as select routine_schema, routine_name from information_schema.routines 
+order by routine_schema, routine_name;
+select * from v1;
+routine_schema	routine_name
+test	sel2
+test	sub1
+drop view v1;
 select ROUTINE_NAME, ROUTINE_DEFINITION from information_schema.ROUTINES;
 ROUTINE_NAME	ROUTINE_DEFINITION
 show create function sub1;

mysql-test/t/information_schema.test

@@ -142,6 +142,11 @@ select a.ROUTINE_NAME, b.name from information_schema.ROUTINES a,
 mysql.proc b where a.ROUTINE_NAME = convert(b.name using utf8) order by 1;
 select count(*) from information_schema.ROUTINES;
 
+create view v1 as select routine_schema, routine_name from information_schema.routines 
+order by routine_schema, routine_name;
+select * from v1;
+drop view v1;
+
 connect (user1,localhost,mysqltest_1,,);
 connection user1;
 select ROUTINE_NAME, ROUTINE_DEFINITION from information_schema.ROUTINES;

sql/sql_show.cc

@@ -3864,7 +3864,8 @@ bool get_schema_tables_result(JOIN *join)
     TABLE_LIST *table_list= tab->table->pos_in_table_list;
     if (table_list->schema_table && thd->fill_derived_tables())
     {
-      bool is_subselect= (&lex->unit != lex->current_select->master_unit());
+      bool is_subselect= (&lex->unit != lex->current_select->master_unit() &&
+                          lex->current_select->master_unit()->item);
       /*
         The schema table is already processed and 
         the statement is not a subselect.