Unload current wallet when clicking "change another wallet"

[brandonbevans]

Currently, when you click "change another wallet", a wallet that's currently loaded will stay loaded until another wallet file is selected. Sometimes I just want to unload the current wallet so that it's not unlocked. Clicking change wallet should immediately lock and clear an existing unlocked wallet.

[yupnano]

A good suggestion, we need to add a button to remove current wallet account.