Failed to authenticate: anonymous

I extended entity sec$User. I added one field - association many-to-one.
Now when I starting application I get
09:16:46.720 ERROR - Unable to login anonymous session Unknown login name or bad password: anonymous
at [cuba-core-6.5.5.jar:6.5.5]
I upgrade cuba to version 6.5.5.
What can I do ???

Could you specify when the extended entity was created - after the migration or before? Also, could you clarify if your new attribute is mandatory? Please, check that there is the anonymous user in the database.

I extended entity before migration. My new attribute isn’t mandatory. There is the anonymous user in the database.

I did migration because of this error. I’ve read that from cuba 6.5 something changed with authentication .