kivy: show error message with qr scanner

gui/kivy/main_window.py

@@ -317,6 +317,12 @@ class ElectrumWindow(App):
                     contents = intent.getStringExtra("SCAN_RESULT")
                     if intent.getStringExtra("SCAN_RESULT_FORMAT") == 'QR_CODE':
                         on_complete(contents)
+                    else:
+                        self.show_error("wrong format " + intent.getStringExtra("SCAN_RESULT_FORMAT"))
+                else:
+                    self.show_error("wrong resultCode %d" % resultCode)
+            else:
+                self.show_error("wrong requestCode %d" % requestCode)
         activity.bind(on_activity_result=on_qr_result)
         try:
             PythonActivity.mActivity.startActivityForResult(intent, 0)