Finance: improve "almost" empty states

[sohkai]

Two "almost" empty states are possible for the Finance app:

1. User has prior transactions, but no balance left because everything has been transferred out:

2. User has transferred ETH directly to the Vault, without making any prior transactions with the Finance app:

Both of these cases should be fairly rare, but they do look a bit odd. Especially with 1. it might be nice to have a toggle or option to see all tokens you've previously held in the balances, even if their balance is now 0.

[sohkai]

Will be fixed in 0.8.