Extra item added to the list and can't remove an item when unchecking; if user change the 'War Era'

[sdgun]

Target URL

http://127.0.0.1:5000/configuration/create

Steps to Reproduce

1. Open the URL http://127.0.0.1:5000/
2. Click 'Create Configuration'
3. Fill all the required data and select War Era as 'Korea'
4. Click NEXT
5. Select first 3 items and add to the list
6. Click ' POPULATION AND DATA SCOPE'
7. Select War Era as 'Gulf War'
8. Click NEXT
9. Expand the list and try to Uncheck the current item
10. Then Select another item and click Add
11. Check the list

Actual Result(s)

• Extra item added to the list and can't remove an item when unchecking; if user change the 'War Era'

Expected Result(s)

• User must able to remove an item by unchecking it from the list
• Must not add duplicate items to the list

Frequency

• 5/5

Environment Details

• Device(s): Laptop
• Resolution: 1366 x 768
• Operating System: Windows 7 64bit
• Browser(s): Chrome 66.0.3359.117 (Official Build) (64-bit)

Image(s)/Video(s)/Console Log/Crash Log

Video: https://www.screencast.com/t/JoHtWh5vSK

[ksmacleod99]

Corrected by PR #54