Pull request #3679: 无JIRA任务，优化object对象的un方法

Merge in VISUAL/fineui from ~FANGLEI/fineui:master to master

* commit '50d43612d4d71a190c4adb2b382fa3c7dd92f882':
  无JIRA任务，优化object对象的un方法

packages/fineui/src/core/3.ob.js

@@ -155,7 +155,7 @@ export class OB {
         eventName = eventName.toLowerCase();
 
         /* alex:如果fn是null,就是把eventName上面所有方法都un掉*/
-        if (fn === null) {
+        if (!fn) {
             delete this._getEvents()[eventName];
         } else {
             const fns = this._getEvents()[eventName];