Check whether data store is initialized before trying to remove expired items.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@549 44740490-163a-0410-bde0-09ae8108e29a

lib/SimpleSAML/Session.php

@@ -507,6 +507,10 @@ class SimpleSAML_Session implements SimpleSAML_ModifiedInfo {
 	 */
 	private function expireData() {
 
+		if(!is_array($this->dataStore)) {
+			return;
+		}
+
 		$ct = time();
 
 		foreach($this->dataStore as &$typedData) {