ob-sh: detect tables correctly

* lisp/ob-sh.el (org-babel-sh-var-to-sh): When detecting a table, the
  first line could be the symbol `hline' rather than a list of table
  cells, so check for that as well.

Thanks to Paul Stansell for pointing out the error.

lisp/ob-sh.el

@@ -106,7 +106,7 @@ var of the same value."
   "Convert an elisp value to a string."
   (let ((echo-var (lambda (v) (if (stringp v) v (format "%S" v)))))
     (cond
-     ((and (listp var) (listp (car var)))
+     ((and (listp var) (or (listp (car var)) 'hline))
       (orgtbl-to-generic var  (list :sep (or sep "\t") :fmt echo-var)))
      ((listp var)
       (mapconcat echo-var var "\n"))