File "electrum/gui/qt/main_window.py", line 1444, in spend_max
  File "electrum/gui/qt/main_window.py", line 1440, in <lambda>
  File "electrum/wallet.py", line 1404, in make_unsigned_transaction
  File "electrum/wallet.py", line 216, 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