fix debug output for list of match expressions

lib/matcher/ListOfMatchExpression.js

@@ -86,9 +86,12 @@ proto.getChildVector = function getChildVector(){
  * @param level
  *
  */
-proto._debugList = function _debugList(debug, level){
-	for (var i = 0; i < this._expressions.length; i++ )
-		this._expressions[i].debugString(debug, level + 1);
+proto._debugList = function _debugList(level){
+	var s = "";
+	for (var i = 0; i < this._expressions.length; i++) {
+		s += this._expressions[i].debugString(level + 1);
+	}
+	return s;
 };
 
 /**