libgit2 segfault on git_checkout_tree()

segfault.c

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <git2.h>

int main(int argc, char* argv[])
{
  git_repository* p_repo;
  git_reference* p_ref;
  git_reference* p_head;
  const git_oid* p_oid;
  git_commit* p_commit;
  git_checkout_opts opts;
  git_strarray ary;
  char hash[41];

  memset(hash, 0, 41);
  ary.count = 0;

  opts.checkout_strategy = GIT_CHECKOUT_DEFAULT; /* GIT_CHECKOUT_OVERWRITE_MODIFIED | GIT_CHECKOUT_CREATE_MISSING | GIT_CHECKOUT_REMOVE_UNTRACKED; */
  opts.disable_filters = 0;
  opts.dir_mode = 0755;
  opts.file_mode = 0644;
  opts.file_open_flags = O_CREAT | O_TRUNC | O_WRONLY;
  opts.notify_payload = NULL;
  opts.paths = ary;

  printf("Opening repository... ");
  git_repository_open(&p_repo, "foo/.git");
  printf("Done.\n");

  printf("Looking up refs/heads/master... ");
  git_reference_lookup(&p_ref, p_repo, "refs/heads/master");
  p_oid = git_reference_oid(p_ref);
  git_oid_fmt(hash, p_oid);

  printf("Resolves to %s\n", hash);
  git_commit_lookup(&p_commit, p_repo, p_oid);

  printf("Updating working tree... ");
  git_checkout_tree(p_repo, (git_object*)p_commit, &opts, NULL);
  printf("Done.\n");
	
  printf("Adjusting HEAD... ");
  git_reference_lookup(&p_head, p_repo, "HEAD");
  git_reference_set_target(p_head, "refs/heads/master");
  printf("Now points to %s.\n", git_reference_target(p_head));

  printf("Freeing stuff.\n");
  git_reference_free(p_head);
  git_commit_free(p_commit);
  git_reference_free(p_ref);
  git_repository_free(p_repo);
  return 0;
}