BUG Find Form actions in CompositeFields for access checks

This bug was introduced with the new nested CMS actions
around December 2012, but wasn't noticed until now
because checkAccessAction() would wrongly return TRUE
before the dataFieldByName() check was reached.

forms/Form.php

@@ -289,7 +289,7 @@ public function httpSubmission($request) {
 			$this->controller->hasMethod($funcName)
 			&& !$this->controller->checkAccessAction($funcName)
 			// If a button exists, allow it on the controller
-			&& !$this->actions->fieldByName('action_' . $funcName)
+			&& !$this->actions->dataFieldByName('action_' . $funcName)
 		) {
 			return $this->httpError(
 				403,