kbx: Fix checksum computation for no UBID entry on disk.
* kbx/keybox-blob.c (create_blob_header): Fix the flag to match no UBID entry, (create_blob_finish): Fix the length of data to be hashed.
- GnuPG-bug-id: T5573
- Fixes-commit: 915297705af6f1db74dacf0d6665b83eb0a58459
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>