FullCalendar refetchEvents无法读取null的属性“format”

Question

当我尝试在保存后从Fullcalendar重新获取事件时，我在fullcalendar.min.js中得到以下错误：6。 为什么我会收到此错误？

HashMap<String, String[]> myObjectStore3 = new HashMap<String, String[]>();

String[] directReports3 = new String[]{"Natraj G", "Kalyan", "Mahitha"}; 

myObjectStore3.put("emp_id", new String[]{123 + ""});
myObjectStore3.put("salary", new String[]{32312 + ""}); 
myObjectStore3.put("directReports", directReports3);

我将事件用作json feed：

Uncaught TypeError: Cannot read property 'format' of null