MDEV-34880 Incorrect result for query with derived table having TEXT field

Fixup: check key flags only in the case of successful index initialization

Author: Olernov

sql/handler.cc

@@ -3749,11 +3749,11 @@ int handler::ha_index_init(uint idx, bool sorted)
     inited=       INDEX;
     active_index= idx;
     end_range= NULL;
+    /*
+      Do not allow reads from UNIQUE HASH indexes.
+    */
+    DBUG_ASSERT(!(table->key_info[active_index].flags & HA_UNIQUE_HASH));
   }
-  /*
-    Do not allow reads from UNIQUE HASH indexes.
-  */
-  DBUG_ASSERT(!(table->key_info[active_index].flags & HA_UNIQUE_HASH));
 
   DBUG_RETURN(result);
 }