It turns out we deploy butterfly net with an account actor. In such a case the migration passes because we don't check f090's pre migration code cid, just set its code cid post migration. The problem that arises with this is that the delegated address is kept in state which allows sends to continue working after the migration.
This PR isn't critical for mainnet state since in mainnet f090 is a multisig with delegated address == nil. So there could be no such spending post migration. However its cleaner to follow the f099 path and set delegated address to the id address of the actor. This has the benefit of giving the expected behavior on testnetworks that want to set up f090 as both a large canonical store of FIL and an account actor.
It turns out we deploy butterfly net with an account actor. In such a case the migration passes because we don't check f090's pre migration code cid, just set its code cid post migration. The problem that arises with this is that the delegated address is kept in state which allows sends to continue working after the migration.
This PR isn't critical for mainnet state since in mainnet f090 is a multisig with delegated address == nil. So there could be no such spending post migration. However its cleaner to follow the f099 path and set delegated address to the id address of the actor. This has the benefit of giving the expected behavior on testnetworks that want to set up f090 as both a large canonical store of FIL and an account actor.