bug#48359: 28.0.50; vc-annotate revert doesn't work

[Dima Kogan]

Hi. This should be simple, but I can't figure it out quickly. Can I get
another set of eyes?

Using a very recent emacs built from git.

Recipe:

1. emacs -Q -nw file_in_a_git_repo
   Any file in any repo works probably. I'm using ~/.emacs.d/init.el

2. C-x v g
   vc-annotate

3. g
   Should "revert" the annotation buffer

This last step doesn't work: I get

  apply: Symbol's function definition is void: nil

Looking into that, I see that 'g' maps to (revert-buffer), which makes
sense. For some reason, revert-buffer-function is set to
#'help-mode-revert-buffer. This feels very strange. And is the cause of
the error: help-mode-revert-buffer assumes we're looking at a Help
buffer, and tries to call nil as a function. Is this speaking to anybody?

Thanks