qt wizard: fix scanning qr code when restoring from xpub

fixes #6342

electrum/gui/qt/qrtextedit.py

@@ -60,9 +60,9 @@ class ScanQRTextEdit(ButtonsTextEdit, MessageBoxMixin):
 
     def qr_input(self):
         from electrum import qrscanner
-        main_window = get_parent_main_window(self)
-        assert main_window
-        config = main_window.config
+        window_or_wizard = get_parent_main_window(self, allow_wizard=True)
+        assert window_or_wizard
+        config = window_or_wizard.config
         try:
             data = qrscanner.scan_barcode(config.get_video_device())
         except BaseException as e:

electrum/gui/qt/util.py

@@ -30,6 +30,7 @@ from electrum.invoices import PR_UNPAID, PR_PAID, PR_EXPIRED, PR_INFLIGHT, PR_UN
 
 if TYPE_CHECKING:
     from .main_window import ElectrumWindow
+    from .installwizard import InstallWizard
 
 
 if platform.system() == 'Windows':
@@ -945,19 +946,23 @@ def export_meta_gui(electrum_window, title, exporter):
                                      .format(title, str(filename)))
 
 
-def get_parent_main_window(widget):
+def get_parent_main_window(
+        widget, *, allow_wizard: bool = False,
+) -> Union[None, 'ElectrumWindow', 'InstallWizard']:
     """Returns a reference to the ElectrumWindow this widget belongs to."""
     from .main_window import ElectrumWindow
     from .transaction_dialog import TxDialog
+    from .installwizard import InstallWizard
     for _ in range(100):
         if widget is None:
             return None
         if isinstance(widget, ElectrumWindow):
             return widget
-        elif isinstance(widget, TxDialog):
+        if isinstance(widget, TxDialog):
             return widget.main_window
-        else:
-            widget = widget.parentWidget()
+        if isinstance(widget, InstallWizard) and allow_wizard:
+            return widget
+        widget = widget.parentWidget()
     return None