Backport commit 2fde6275b from Emacs

* lisp/ob-core.el (org-babel-insert-result): Use proper-list-p.

Add predicate proper-list-p
2fde6275b69fd113e78243790bf112bbdd2fe2bf
Basil L. Contovounesios
Mon Jul 9 19:00:43 2018 -0700

lisp/ob-core.el

@@ -2320,10 +2320,9 @@ INFO may provide the values of these header arguments (in the
 		       (lambda (r)
 			 ;; Non-nil when result R can be turned into
 			 ;; a table.
-			 (and (listp r)
-			      (null (cdr (last r)))
+                         (and (proper-list-p r)
 			      (cl-every
-			       (lambda (e) (or (atom e) (null (cdr (last e)))))
+                               (lambda (e) (or (atom e) (proper-list-p e)))
 			       result)))))
 		  ;; insert results based on type
 		  (cond