6ed424f2db wallet: fix, detect blank legacy wallets in IsLegacy (furszy)
Pull request description:
Blank legacy wallets do not have active SPKM. They can only be
detected by checking the descriptors' flag or the db format.
This enables the migration of blank legacy wallets in the GUI.
To test this:
1) Create a blank legacy wallet.
2) Try to migrate it using the GUI's toolbar "Migrate Wallet" button.
-> In master: The button will be disabled because `CWallet::IsLegacy()` returns false for blank legacy wallet.
-> In this PR: the button will be enabled, allowing the migration of legacy wallets.
ACKs for top commit:
achow101:
ACK 6ed424f2db
tdb3:
ACK 6ed424f2db
glozow:
ACK 6ed424f2db
Tree-SHA512: c06c4c4c2e546ccb033287b9aa3aee4ca36b47aeb2fac6fbed5de774b65caef9c818fc8dfdaac6ce78839b2d5d642a5632a5b44c5e889ea169ced80ed50501a7
ee367170cb