Pull request #3299: 无jira fix(base/extend): 修改泛型

Merge in VISUAL/fineui from ~XAVIER.MENG/fineui:master to master

* commit '2bff8dc7884f418895adf57cd58eabd98d7b1926':
  无jira fix(base/extend): 修改泛型

typescript/core/base.ts

@@ -178,7 +178,7 @@ export interface _base {
     functions: (object: object) => string[];
 
     extend<T extends object>(object: T): T;
-    extend<T extends object, U extends object>(object: T, ...sources: U[]): T & UnionToIntersection<U>;
+    extend<T extends object, U>(object: T, ...sources: U[]): T & UnionToIntersection<NonNullable<U>>;
 
     defaults: (object: object, ...sources: any[]) => object;