File "electrum\gui\qt\main_window.py", line 1438, in spend_max
  File "electrum\gui\qt\main_window.py", line 1434, in <lambda>
  File "electrum\wallet.py", line 1273, in make_unsigned_transaction
  File "electrum\wallet.py", line 209, in get_locktime_for_new_transaction
  File "electrum\blockchain.py", line 490, in is_tip_stale
  File "electrum\blockchain.py", line 486, in header_at_tip
  File "electrum\blockchain.py", line 201, in func_wrapper
  File "electrum\blockchain.py", line 478, in read_header