fix a stray "user-error" introduced in bd89d6a02f

* lisp/org-table.el (org-table-eval-formula): The condition-case to
  check for must be "error", not "user-error".

This fixes these test failures:

4 unexpected results:
   FAILED  test-org-table/references/format-specifier-E
   FAILED  test-org-table/references/format-specifier-EL
   FAILED  test-org-table/references/format-specifier-L
   FAILED  test-org-table/references/format-specifier-none

Reported in:
http://permalink.gmane.org/gmane.emacs.orgmode/67450
http://permalink.gmane.org/gmane.emacs.orgmode/67503

lisp/org-table.el

@@ -2705,7 +2705,7 @@ not overwrite the stored one."
 	(if lispp
 	    (setq ev (condition-case nil
 			 (eval (eval (read form)))
-		       (user-error "#ERROR"))
+		       (error "#ERROR"))
 		  ev (if (numberp ev) (number-to-string ev) ev)
 		  ev (if duration (org-table-time-seconds-to-string
 				   (string-to-number ev)