privent crash on temporary table during indexes lookup (BUG#4677)

mysql-test/r/view.result:
  check 'use index' on view with temporary table
mysql-test/t/view.test:
  check 'use index' on view with temporary table
sql/sql_base.cc:
  privent crash on temporary table

mysql-test/r/view.result

@@ -977,3 +977,9 @@ ERROR HY000: View 'test.v1' references invalid table(s) or column(s)
 drop view v1;
 create view v1 (a,a) as select 'a','a';
 ERROR 42S21: Duplicate column name 'a'
+create table t1 (a int, b int);
+create view v1 as select a, sum(b) from t1 group by a;
+select b from v1 use index (some_index) where b=1;
+ERROR 42000: Key column 'some_index' doesn't exist in table
+drop view v1;
+drop table t1;

mysql-test/t/view.test

@@ -900,3 +900,13 @@ drop view v1;
 #
 -- error 1060
 create view v1 (a,a) as select 'a','a';
+
+#
+# check 'use index' on view with temporary table
+#
+create table t1 (a int, b int);
+create view v1 as select a, sum(b) from t1 group by a;
+-- error 1072
+select b from v1 use index (some_index) where b=1;
+drop view v1;
+drop table t1;

sql/sql_base.cc

@@ -2555,8 +2555,9 @@ bool get_key_map_from_key_list(key_map *map, TABLE *table,
   map->clear_all();
   while ((name=it++))
   {
-    if ((pos= find_type(&table->keynames, name->ptr(), name->length(), 1)) <=
-	0)
+    if (table->keynames.type_names == 0 ||
+        (pos= find_type(&table->keynames, name->ptr(), name->length(), 1)) <=
+        0)
     {
       my_error(ER_KEY_COLUMN_DOES_NOT_EXITS, MYF(0), name->c_ptr(),
 	       table->real_name);