Traceback (most recent call last):
  File "electrum\gui\qt\my_treeview.py", line 308, in mouseDoubleClickEvent
  File "electrum\gui\qt\invoice_list.py", line 89, in on_double_click
  File "electrum\gui\qt\invoice_list.py", line 148, in show_invoice
  File "electrum\gui\qt\main_window.py", line 1412, in show_onchain_invoice
  File "electrum\gui\qt\main_window.py", line 1412, in <lambda>
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'