hw wallets: handle cancellation for "query_choice" in wizard

E | gui.qt.exception_window.Exception_Hook | exception caught by crash reporter
Traceback (most recent call last):
  File "...\electrum\electrum\plugins\hw_wallet\qt.py", line 193, in win_query_choice
    self.choice = self.win.query_choice(msg, labels)
  File "...\electrum\electrum\gui\qt\installwizard.py", line 545, in query_choice
    self.exec_layout(vbox, '')
  File "...\electrum\electrum\gui\qt\installwizard.py", line 392, in exec_layout
    raise UserCancelled
electrum.util.UserCancelled

electrum/plugins/hw_wallet/qt.py

@@ -190,7 +190,10 @@ class QtHandlerBase(HardwareHandlerBase, QObject, Logger):
             self.dialog = None
 
     def win_query_choice(self, msg, labels):
-        self.choice = self.win.query_choice(msg, labels)
+        try:
+            self.choice = self.win.query_choice(msg, labels)
+        except UserCancelled:
+            self.choice = None
         self.done.set()
 
     def win_yes_no_question(self, msg):