Include nil as valid wallpaper-commmand

* lisp/image/wallpaper.el (wallpaper-command):
Include nil in the type since that is a valid value for the variable,
and may be the default value.  This should fix test-custom-opts.

diff --git a/lisp/image/wallpaper.el b/lisp/image/wallpaper.el
index 16fc9d23ecb2d14f56c3bbeb00ee480ac3d4445f..9572349c366b671a013526602514287c53fa9d0b 100644 (file)
--- a/lisp/image/wallpaper.el
+++ b/lisp/image/wallpaper.el
@@ -167,7 +167,8 @@ systems, where a native API is used instead."
      (const :tag "xloadimage                  (X Window System)"  "xloadimage")
      (const :tag "xsetbg                      (X Window System)"  "xsetbg")
      (const :tag "osascript                   (macOS)"            "osascript"))
-    (const :tag "Other (specify)"         string))
+    (const :tag "Other (specify)"         string)
+    (const :tag "None" nil))
   :set #'wallpaper--set-wallpaper-command
   :group 'image
   :version "29.1")