commit 8ec0bb76ea97b6f2a998ae6e602644601fda872d
from: Omar Polo <op@omarpolo.com>
date: Wed Aug 11 17:34:52 2021 UTC

guard vc-got-diff against nil files

commit - 6a973a79a08fc69b9f5a6d69edb012ab97854ba3
commit + 8ec0bb76ea97b6f2a998ae6e602644601fda872d
blob - bb56d0b4000f341d2fa5335ec3a5588897c88d22
blob + 003d62abccc3cac7797d31141cb8a3d5def983b0
--- vc-got.el
+++ vc-got.el
@@ -721,7 +721,8 @@ Heavily inspired by `vc-git-log-view-mode'."
   (let* ((buffer (get-buffer-create (or buffer "*vc-diff*")))
          (inhibit-read-only t))
     (with-current-buffer buffer
-      (vc-got-with-worktree (car files)
+      (vc-got-with-worktree (or (car files)
+                                default-directory)
         (if (and (null rev1)
                  (null rev2))
             (dolist (file files)