--- typo3-6.1.7/typo3/sysext/form/Classes/Domain/Model/Attribute/AttributesAttribute.php	2014-02-26 16:51:23.000000000 +0100
+++ typo3-6.1.7/typo3/sysext/form/Classes/Domain/Model/Attribute/AttributesAttribute.php	2014-04-09 13:51:18.529238554 +0200
@@ -148,9 +148,13 @@
 	 * @return string The content of the attribute
 	 */
 	public function getValue($key) {
+		if (! is_object($this->getAttributeObjectByKey($key)))
+		{
+			return null;
+		}
 		return $this->getAttributeObjectByKey($key)->getValue();
 	}
 
 }