Hide Hardware wallet accounts when hardware wallet disconnected

When a hardware wallet is added and then unplugged the account is still visible and selected.
Attempting a transaction on this account results in the following errors:
```
Error: Returned error: Error: [object Object]
MetaMask - RPC Error: TypeError: Cannot use 'in' operator to search for 'from' in null
```
Is it possible to hide these accounts when the hardware is not plugged in or return a more meaningful error the Dapp can react to ?

Start by reproducing the unplugged hardware-wallet scenario described in the issue and inspect the path that keeps the account selected after disconnection. Compare the two proposed outcomes: hiding unavailable accounts or returning a Dapp-actionable error. Done means the disconnected account is no longer usable and the transaction attempt no longer produces the reported null-related error.

Written by the indexing model from the issue text.