r1165752 | stsp | 2011-09-06 11:26:30 -0500 (Tue, 06 Sep 2011)

On the fs-successor-ids branch, write successor-IDs for empty revisions, too.

Not writing successors for empty revisions violates a constraint of the
design: Every revision needs to be recorded in db/successors/revs/* files
so that offsets can be computed correctly.

Found by: danielsh.

* subversion/libsvn_fs_fs/fs_fs.c
  (commit_body): Update successor map even if the successor IDs hash is empty.