The function dict_stats_process_entry_from_defrag_pool() fails to invoke dict_table_close() when an index does not exist in the table (for example because it has been dropped):

	dict_index_t*	index = dict_table_find_index_on_id(table, index_id);

	if (index == NULL) {

		return;

	}

	/* Check whether index is corrupted */

	if (dict_index_is_corrupted(index)) {

		dict_table_close(table, FALSE, FALSE);

		return;

	}

As you can see above, existing but corrupted indexes are handled correctly.

Failure to release a table handle should cause an infinite wait at some point in InnoDB, at least in DROP TABLE:

2017-12-02 21:06:52 139784064132864 [Warning] InnoDB: Waited 270 seconds for ref-count on table: `db`.`tablename` space: 12345