Inconsistent scroll behind popup

Reproduction Steps:

1. Open the application: https://skill-search.topcoder-dev.com/
2. Click on any "+" button -> show "Add to group" popup
3. Try to scroll down/up page then observe
4. Click on "Cancel" button
5. Click on any "Add filter" button -> show "Add filter" popup
6. Try to scroll down/up page then observe

Screenshot/screencast: https://drive.google.com/drive/folders/1YKCNzbN5iK6NHyzaJOyj85frC1i0Qg75

Actual Result: "Inconsistent scroll behind popup. Step 3: User can't scroll down/up page Step 6: User can scroll down/up page

Expected Result: "Should consistent scroll behind popup.

Device/OS: Laptop | Windows 10 (64bit)

Browser Information: IE11 , Google Chrome 83.0.4103.116, Firefox 78.0.2

Final Submission Guidelines

Git issue link: https://github.com/topcoder-platform/u-bahn-app/issues/144