filter_sparse_oid__init() uses add_patterns_from_blob_to_list() to
populate the struct pattern_list member of struct filter_sparse_data.
Release it in the complementing filter_sparse_free().
Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>