Does not work with empty commits

[AnthonyMastrean]

I was just trying to troll a coworker, so I made an empty commit.

$ git commit --allow-empty -m ':)'

But, vanity-sha didn't like changing that commit.

$ git vanity-sha cafe
Searching for new SHA...
SHA found: cafe057fa380a5976440013ce29703385c8ccd89
Change committer timestamp to 2019-07-04 20:06:22 +0000? This will amend your commit.
(y/n): y
You asked to amend the most recent commit, but doing so would make
it empty. You can repeat your command with --allow-empty, or you can
remove the commit entirely with "git reset HEAD^".

-----------------------------------------------
commit e3b531fc6e593f6b3345630e51fe4f248aacc98e
Author: Anthony Mastrean <anthony.mastrean@gmail.com>

    :)