It happened to me to sleep inside a doorless Ice Fishing Hut overnight. I then got the message "something woke you up" and found a bear standing on the front door. It appeared it didn't fit trough the opening (while standing, it was too tall).
Then it got around the hut, I could hear it snort and roar, but it didn't attack me. I don't know if it's a coincidence or if fishing huts actually repel bears as well.