I will see if I can find a workaround for it on 24.5.
Here's a final try ..
Please replace the advising function with this one:
(defun modi/org-insert-org-entity-maybe (orig-fun &rest args)
"When the universal prefix C-u is used before entering any character,
insert the character's `org-entity' name if available."
(let ((pressed-key (char-to-string (elt (this-single-command-keys) 0)))
entity-name)
(when (and (listp args) (eq 4 (car args)))
(setq entity-name (modi/org-entity-get-name pressed-key))
(when entity-name
(setq entity-name (concat "\\" entity-name "{}"))
(insert entity-name)
(message (concat "Inserted `org-entity' "
(propertize entity-name
'face 'font-lock-function-name-face)
" for the symbol "
(propertize pressed-key
'face 'font-lock-function-name-face)
"."))))
(when (null entity-name)
(apply orig-fun args))))
The only change is in this line:
(let ((pressed-key (char-to-string (elt (this-single-command-keys) 0)))
I have quickly verified it to work the same in both emacs 24.5 and emacs 25.x.
Let me know. Thanks for testing the code.