Checkbox covers selection list.

Steps:

1. Log in as admin.
2. Go to Admin / Content Types / Content.
3. Create new Content type.
4. Add Selection field type with several options.
5. Add Checkbox field type.
6. Save.
7. Go to Content / Content structure.
8. Create new Content item using the Content type.
9. Expand the selection list.

Issue: Checkbox covers the list.