Hi Vinod,

The alert says that the value of key 'TaskIndex' is not available, so an exception is thrown by safeurl.put method.

Can you check what is the action configured on the button, if you are running some script then handle the null value check in the method:

eg: if(TaksIndex != undefined){

Osafeurl.put("TaskIndex", TaskIndex);

}

Hope it helps.

Thanks.