hw wallets: test client is not None during setup_device

plugins/ledger/ledger.py

@@ -585,6 +585,9 @@ class LedgerPlugin(HW_PluginBase):
         devmgr = self.device_manager()
         device_id = device_info.device.id_
         client = devmgr.client_by_id(device_id)
+        if client is None:
+            raise Exception(_('Failed to create a client for this device.') + '\n' +
+                            _('Make sure it is in the correct state.'))
         client.handler = self.create_handler(wizard)
         client.get_xpub("m/44'/0'", 'standard') # TODO replace by direct derivation once Nano S > 1.1