Traceback (most recent call last):
  File "electrum\gui\qt\send_tab.py", line 536, in do_save_invoice
  File "electrum\gui\qt\send_tab.py", line 514, in read_invoice
  File "electrum\gui\qt\send_tab.py", line 629, in check_payto_line_and_show_errors
AttributeError: 'NoneType' object has no attribute 'get_error'