Comment 22 for bug 128624

#0 0x0000000000e1a012 in strcmp () from /lib64/libc.so.6
        mallstream = (FILE *) 0x0
        tr_old_memalign_hook = (void *(*)(size_t, size_t, const void *)) 0
        tr_old_malloc_hook = (void *(*)(size_t, const void *)) 0
        tr_old_realloc_hook = (void *(*)(void *, size_t, const void *)) 0
        lock = 0
        mallenv = "MALLOC_TRACE"
        malloc_trace_buffer = 0x0
        tr_old_free_hook = (void (*)(void *, const void *)) 0
        mallwatch = (void *) 0x0
#1 0x00007fb31467abee in find_generic_function (table=0x7fb3155893f0, key=0x7fb3155973b0, idx=10,
    compare_func=0xe1a010 <strcmp>, create_if_not_found=1, bucket=0x0, preallocated=0x7fb315607828)
    at dbus-hash.c:918
        entry = (DBusHashEntry *) 0x7fb3156077f8
#2 0x00007fb31467aea6 in find_string_function (table=0x7fb3155893f0, key=0x7fb3155973b0,
    create_if_not_found=1, bucket=0x0, preallocated=0x7fb315607828) at dbus-hash.c:952
No locals.
#3 0x00007fb31467a8b1 in _dbus_hash_table_insert_string_preallocated (table=0x7fb3155973b0,
    preallocated=0x7fb315607828, key=0x7fb3155973b0 "developer", value=0x7fb3155ab350) at dbus-hash.c:1680
        entry = <value optimized out>
#4 0x00007fb31467aad9 in _dbus_hash_table_insert_string (table=0x7fb3155893f0,
    key=0x7fb3155973b0 "developer", value=0x7fb3155ab350) at dbus-hash.c:1443
        preallocated = (DBusPreallocatedHash *) 0xffffff64
#5 0x00007fb31468171e in _dbus_user_database_lookup (db=0x7fb315589260, uid=500, username=0x7fb3155e9fb0,

Seems it's different with #bug 15588, From the above backtrace, it fail due to update userdb table, after #bug 15588 fixed, this can only happen if compiling with "--disable-userdb-cache" because it still try to update userdb hash table, this is not necessary because userdb cache disabled by user.

So here is a patch to fix it.