Error when loading application after deleting wallet

[AaronFeickert]

To reproduce:

• Create a single wallet.
• Delete the wallet, so no wallets remain.
• Close the application.
• Start the application, entering the password.

Expected behavior: The application loads, showing no wallets.

Actual behavior: An error message occurs, indicating the "given wallet doesn't exist".

[MrCyjaneK]

Thanks for the report, the issue should be fixed in this PR: https://github.com/cake-tech/cupcake/pull/10