Expecting you do not want to add leased address to an address list.
Seems there is a bug. If you populate the address list field of some lease and press ok, then if you open it and “hide” the field address list and press ok again, the field vanishes, the value vanishes from export and from print command but it is still active there.
Solution:
Open the lease, unhide the field address list, delete the content and press ok.
If it helps, send e-mail to support@mikrotik.com and report a bug.