Possible migration problem in migrateInfosNotificationsNotDesired

It seems that when a disabled subscriber entry is already present (possibly when doing a migration rerun, or when a user disabled a subscription when the migration did not finish yet) a unique key constraint is violated by creating a new entry. I don't see the point in creating an entry in this case anyway so we are disabling it, see also:
https://git.uibk.ac.at/zid/dmlt/olat/openolat/commit/0f1596ccd73ac6dc85749c4b7b023ed2085a3451