Empty closed:note key in changeset tags

[ygra]

When not closing a note, this sometimes happens: https://www.openstreetmap.org/changeset/132703728

JOSM complains about it, and I decided to look whether it would actually appear in the changeset tags. Yes, it does, and it's empty.

[kmpoppe]

... and I always thought the API would prevent empty keys AND I thought I had prevented adding the field when the value was empty.

I seem to have been mistaken on both accounts 🤦‍♂️