use dictionary for reduce object list

underscore/underscore.d.ts

@@ -180,7 +180,7 @@ interface UnderscoreStatic {
 		context?: any): TResult;
 
 	reduce<T, TResult>(
-		list: _.Collection<T>,
+		list: _.Dictionary<T>,
 		iterator: _.ObjectIterator<T, TResult>,
 		memo?: TResult,
 		context?: any): TResult;