File "electrum\gui\qt\main_window.py", line 3025, in closeEvent
  File "electrum\gui\qt\main_window.py", line 3042, in clean_up
  File "electrum\gui\qt\__init__.py", line 268, in close_window
  File "electrum\simple_config.py", line 287, in save_last_wallet
  File "electrum\simple_config.py", line 142, in set_key
  File "electrum\simple_config.py", line 151, in _set_key_in_user_config
  File "electrum\simple_config.py", line 231, in save_user_config