trezor: create new accounts in non-GUI thread

gui/qt/main_window.py

@@ -1979,7 +1979,6 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
 
     def check_next_account(self):
         if self.wallet.needs_next_account() and not self.checking_accounts:
-            try:
             self.checking_accounts = True
             msg = _("All the accounts in your wallet have received "
                     "transactions.  Electrum must check whether more "
@@ -1987,13 +1986,14 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
                     "it has been used or you give it a name.")
             self.show_message(msg, title=_("Check Accounts"))
             self.create_next_account()
-                self.update_new_account_menu()
-            finally:
-                self.checking_accounts = False
 
     @protected
     def create_next_account(self, password):
-        self.wallet.create_next_account(password)
+        def on_done():
+            self.checking_accounts = False
+            self.update_new_account_menu()
+        task = partial(self.wallet.create_next_account, password)
+        self.wallet.thread.add(task, on_done=on_done)
 
     def show_master_public_keys(self):
         dialog = WindowModalDialog(self, "Master Public Keys")