Traceback (most recent call last):
  File "electrum/gui/qt/main_window.py", line 2009, in <lambda>
  File "electrum/gui/qt/main_window.py", line 157, in request_password
  File "electrum/gui/qt/main_window.py", line 1965, in do_sign
AttributeError: 'NoneType' object has no attribute 'add'