If you have run recent master, upgrade will fail with:
```
Cannot migrate account database version 18
```
The final migration is:
```
/* We used to send anchors to the wallet, but set ignored tag. Now we send
* them to external. */
{SQL("UPDATE chain_events"
" SET account_id = (SELECT id FROM accounts WHERE name = 'external')"
" WHERE account_id = (SELECT id FROM accounts WHERE name = 'wallet')"
" AND ignored = 1"), NULL},
```
Which is harmless (we do that upgrade ourselves on migration, but if it's done already that will have no effect).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
f4b7f513ee