var OR_JOIN= this.options.form.getWidgetByName("OR_JOIN");var a= this.options.form.getWidgetByName("TASK_ID"); var b= this.options.form.getWidgetByName("CREATE_TIME");var c= this.options.form.getWidgetByName("CREATE_TIME1");var e= this.options.form.getWidgetByName("LabelTASK_ID");var f= this.options.form.getWidgetByName("LabelCREATE_TIME");var g= this.options.form.getWidgetByName("LabelCREATE_TIME1");var d= this.getValue(OR_JOIN);if(d == "Y"){a.setVisible(true);b.setVisible(true);e.setVisible(true);f.setVisible(true);c.setVisible(false);g.setVisible(false);}else if(d == "N"){c.setVisible(true);g.setVisible(true);a.setVisible(false);b.setVisible(false);e.setVisible(false);f.setVisible(false);}然后报错 :CustomJSError : Cannot read property 'setVisible' of undefined 请问如何解决