Index: Classes/Persistence/LazyLoadingProxy.php
===================================================================
--- Classes/Persistence/LazyLoadingProxy.php	(revision 2689)
+++ Classes/Persistence/LazyLoadingProxy.php	(working copy)
@@ -114,6 +114,9 @@
 	 */
 	public function __call($methodName, $arguments) {
 		$realInstance = $this->_loadRealInstance();
+		if (!is_object($realInstance)) {
+			return NULL;
+		}
 		return call_user_func_array(array($realInstance, $methodName), $arguments);
 	}