pkg_jobs.c, pkg_jobs_check_remote_candidate
line 1216:

    while (pkgdb_it_next(it, &p, PKG_LOAD_BASIC) == EPKG_OK) {
        const char *rdigest;

        pkg_get(p, PKG_DIGEST, &rdigest);

        /* here it is, rdigest can be == NULL!!! */

        if (strcmp(rdigest, digest) != 0) /* here i got segfault, possible due the broken db */
             npkg ++;


pkg update -f solve the issue, but i think it is better, to show some warning, and not die :)