transient--post-command: Clear transient-current-* variables here

These variables are only intended to be accessible by the command that
was invoked as a suffix of a prefix.  It we only clear their values when
we exit the prefix (but not when a non-exiting suffix is done), then the
values remain accessible in timers and while the prefix is suspended
(e.g., while using the minibuffer).

lisp/transient.el

@@ -2528,6 +2528,10 @@ value.  Otherwise return CHILDREN as is."
          t)))
 
 (defun transient--post-command ()
+  (transient--debug 'clear-current)
+  (setq transient-current-prefix nil)
+  (setq transient-current-command nil)
+  (setq transient-current-suffixes nil)
   (unless (transient--premature-post-command)
     (transient--debug 'post-command)
     (transient--with-emergency-exit :post-command
@@ -2576,9 +2580,6 @@ value.  Otherwise return CHILDREN as is."
     (remove-hook 'pre-command-hook  #'transient--pre-command)
     (remove-hook 'post-command-hook #'transient--post-command)
     (advice-remove 'recursive-edit #'transient--recursive-edit))
-  (setq transient-current-prefix nil)
-  (setq transient-current-command nil)
-  (setq transient-current-suffixes nil)
   (let ((resume (and transient--stack
                      (not (memq transient--exitp '(replace suspend))))))
     (unless (or resume (eq transient--exitp 'replace))