fix #3016

gui/qt/transaction_dialog.py

@@ -151,7 +151,10 @@ class TxDialog(QDialog, MessageBoxMixin):
             event.ignore()
         else:
             event.accept()
+            try:
                 dialogs.remove(self)
+            except ValueError:
+                pass  # was not in list already
 
     def show_qr(self):
         text = bfh(str(self.tx))