Traceback (most recent call last):
  File "/tmp/.mount_electri7Jb0A/usr/lib/python3.7/site-packages/electrum/gui/qt/swap_dialog.py", line 152, in on_send_edited
    recv_amount = self.swap_manager.get_recv_amount(send_amount, is_reverse=self.is_reverse)
  File "/tmp/.mount_electri7Jb0A/usr/lib/python3.7/site-packages/electrum/submarine_swaps.py", line 524, in get_recv_amount
    if abs(send_amount - inverted_send_amount) > 1:
TypeError: unsupported operand type(s) for -: 'int' and 'NoneType'