devel/git-cinnabar: unbreak after r531622

../helper/cinnabar-helper.c:195:41: error: too few arguments to function call, expected 5, have 4

st = open_istream(oid, &type, &sz, NULL);
     ~~~~~~~~~~~~                      ^

./streaming.h:11:1: note: 'open_istream' declared here
struct git_istream *open_istream(struct repository *, const struct object_id *,
^

Obtained from: upstream