User is not able to select items (field groups) in navigation menu on the left.

Steps to reproduce:
1. Prepare a custom CT with at least 2 fields (one in content category, other in metadata)
2. Go to Content/Content structure
3. Start creating a new CT (from 1.)

Actual result:
'Metadata' option is not selectable.

Expected result:
It is possible to select other options in navigation menu.