hw plugins: cmdline: fix offline commands for encrypted hw wallets

```
$ ./run_electrum --testnet signmessage -w /home/user/.electrum/testnet/wallets/test_trezor_white_bip84 tb1q5pguna9y2g9y2gsu8r8gmxeye2cefvyly8dg02 heyheyhey -o
  0.84 | W | plugins.jade.jadepy.jade | No module named 'electrum.plugins.jade.jadepy.jade_ble'
  0.84 | W | plugins.jade.jadepy.jade | BLE scanning/connectivity will not be available
  3.73 | E | __main__ | error running command (without daemon)
Traceback (most recent call last):
  File "/home/user/wspace/electrum/electrum/plugins/trezor/clientbase.py", line 151, in get_xpub
    node = trezorlib.btc.get_public_node(self.client, address_n).node
  File "/home/user/.local/lib/python3.10/site-packages/trezorlib/tools.py", line 274, in wrapped_f
    ret = f(*args, **kwargs)
  File "/home/user/.local/lib/python3.10/site-packages/trezorlib/btc.py", line 125, in get_public_node
    return client.call(
  File "/home/user/.local/lib/python3.10/site-packages/trezorlib/tools.py", line 297, in wrapped_f
    return f(client, *args, **kwargs)
  File "/home/user/.local/lib/python3.10/site-packages/trezorlib/client.py", line 260, in call
    resp = self._callback_pin(resp)
  File "/home/user/.local/lib/python3.10/site-packages/trezorlib/client.py", line 186, in _callback_pin
    pin = self.ui.get_pin(msg.type)
  File "/home/user/wspace/electrum/electrum/plugins/trezor/clientbase.py", line 308, in get_pin
    pin = self.handler.get_pin(msg.format(self.device), show_strength=show_strength)
AttributeError: 'NoneType' object has no attribute 'get_pin'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/wspace/electrum/./run_electrum", line 540, in handle_cmd
    result = fut.result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 458, in result
    return self.__get_result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
    raise self._exception
  File "/home/user/wspace/electrum/./run_electrum", line 227, in run_offline_command
    password = get_password_for_hw_device_encrypted_storage(plugins)
  File "/home/user/wspace/electrum/./run_electrum", line 212, in get_password_for_hw_device_encrypted_storage
    return client.get_password_for_storage_encryption()
  File "/home/user/wspace/electrum/electrum/plugin.py", line 523, in wrapper
    return run_in_hwd_thread(partial(func, *args, **kwargs))
  File "/home/user/wspace/electrum/electrum/plugin.py", line 516, in run_in_hwd_thread
    return fut.result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 458, in result
    return self.__get_result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
    raise self._exception
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/user/wspace/electrum/electrum/plugins/hw_wallet/plugin.py", line 260, in get_password_for_storage_encryption
    xpub = self.get_xpub(derivation, "standard")
  File "/home/user/wspace/electrum/electrum/plugin.py", line 523, in wrapper
    return run_in_hwd_thread(partial(func, *args, **kwargs))
  File "/home/user/wspace/electrum/electrum/plugin.py", line 513, in run_in_hwd_thread
    return func()
  File "/home/user/wspace/electrum/electrum/plugins/trezor/clientbase.py", line 150, in get_xpub
    with self.run_flow(creating_wallet=creating):
  File "/home/user/wspace/electrum/electrum/plugins/trezor/clientbase.py", line 89, in __exit__
    self.end_flow()
  File "/home/user/wspace/electrum/electrum/plugins/trezor/clientbase.py", line 82, in end_flow
    self.handler.finished()
AttributeError: 'NoneType' object has no attribute 'finished'
```

run_electrum

@@ -209,6 +209,7 @@ def get_password_for_hw_device_encrypted_storage(plugins: 'Plugins') -> str:
     devmgr = plugins.device_manager
     try:
         client = devmgr.client_by_id(device_info.device.id_)
+        client.handler = client.plugin.create_handler(None)
         return client.get_password_for_storage_encryption()
     except UserCancelled:
         sys.exit(0)