MDEV-35342 Server crashes when creating index on a rocksdb table

Debug assertion, added with MDEV-34880, did not take into account that MyRocks sometimes uses hidden indexes that SQL layer isn't aware of. This commit adds a proper handling for such cases

Author: Olernov

sql/handler.cc

@@ -3761,8 +3761,11 @@ int handler::ha_index_init(uint idx, bool sorted)
  end_range= NULL;
  /*
  Do not allow reads from UNIQUE HASH indexes.
+ (1) MyRocks sometimes uses hidden indexes that SQL layer isn't aware of,
+ skip the check for such cases
  */
- DBUG_ASSERT(!(table->key_info[active_index].flags & HA_UNIQUE_HASH));
+ DBUG_ASSERT(active_index >= table->s->keys || // (1)
+ !(table->key_info[active_index].flags & HA_UNIQUE_HASH));
  }
 
  DBUG_RETURN(result);