org-cycle: Throw an error when `org-cycle-max-level' is not positive

* lisp/org-cycle.el (org-cycle): Avoid cryptic regexp error when
`org-cycle-max-level' is not set to positive integer.

Reported-by: Alain.Cochard@unistra.fr
Link: https://orgmode.org/list/25496.14797.512207.593382@gargle.gargle.HOWL

lisp/org-cycle.el

@@ -336,6 +336,10 @@ same as `S-TAB') also when called without prefix argument."
 	      (and org-cycle-level-after-item/entry-creation
 		   (or (org-cycle-level)
 		       (org-cycle-item-indentation))))
+    (when (and org-cycle-max-level
+               (or (not (integerp org-cycle-max-level))
+                   (< org-cycle-max-level 1)))
+      (user-error "`org-cycle-max-level' must be a positive integer"))
     (let* ((limit-level
 	    (or org-cycle-max-level
 		(and (boundp 'org-inlinetask-min-level)