qt: fix scanning multi (privkeys, addresses) from QR.

electrum/gui/qt/util.py

@@ -680,11 +680,18 @@ class GenericInputHandler:
                 return
             if not data:
                 data = ''
+            try:
                 if allow_multi:
-                new_text = self.text() + data + '\n'  # TODO: unused?
+                    text = self.text()
+                    if data in text:
+                        return
+                    if text and not text.endswith('\n'):
+                        text += '\n'
+                    text += data
+                    text += '\n'
+                    setText(text)
                 else:
                     new_text = data
-                try:
                     setText(new_text)
             except Exception as e:
                 show_error(_('Invalid payment identifier in QR') + ':\n' + repr(e))
@@ -725,11 +732,18 @@ class GenericInputHandler:
             show_error(_("No QR code was found on the screen."))
             return
         data = scanned_qr[0].data
+        try:
             if allow_multi:
-            new_text = self.text() + data + '\n'  # TODO: unused?
+                text = self.text()
+                if data in text:
+                    return
+                if text and not text.endswith('\n'):
+                    text += '\n'
+                text += data
+                text += '\n'
+                setText(text)
             else:
                 new_text = data
-            try:
                 setText(new_text)
         except Exception as e:
             show_error(_('Invalid payment identifier in QR') + ':\n' + repr(e))