Steps to reproduce the problem:

1. Configure the Board to use Remaining Estimate and Time Spent estimation.
2. Go to Plan mode and add a new sprint.
3. Add two issues such as DEMO-4 and DEMO-5:
   • DEMO-4 contain no sub-task.
   • DEMO-5 got one sub-task.
4. Assign 12m to Remaining Estimate for DEMO-5 by clicking the down arrow:
   
5. Next, assign 20m to Remaining Estimate for DEMO-4, then bump into the Javascripts error because the pop up box doesn't closed and the value still refer back to DEMO-5:
   
   

Expected Behavior:

After assign Remaining Estimate value to the issue that contain sub-task, the next issue should not show the pop up box again.