emacs-29 ca5b48fd76d: Fix tmm-mid-prompt :type (Bug#66179)

[Eli Zaretskii]

branch: emacs-29
commit ca5b48fd76db2ab7c154c2db6a7d4a9fb7857f6c
Author: Mauro Aranda <maurooaranda@gmail.com>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix tmm-mid-prompt :type (Bug#66179)
    
    * lisp/tmm.el (tmm-mid-prompt): Allow nil.
---
 lisp/tmm.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/tmm.el b/lisp/tmm.el
index a4058594622..b587b416a35 100644
--- a/lisp/tmm.el
+++ b/lisp/tmm.el
@@ -79,7 +79,8 @@ See the documentation for `tmm-prompt'."
   "String to insert between shortcut and menu item.
 If nil, there will be no shortcuts.  It should not consist only of spaces,
 or else the correct item might not be found in the `*Completions*' buffer."
-  :type 'string)
+  :type '(choice (const :tag "No shortcuts" nil)
+                 string))
 
 (defvar tmm-mb-map nil
   "A place to store minibuffer map.")