File "/usr/lib/python3/dist-packages/electrum/gui/qt/main_window.py", line 1613, in do_pay
    self.do_pay_invoice(self.pending_invoice)
  File "/usr/lib/python3/dist-packages/electrum/gui/qt/main_window.py", line 1627, in do_pay_invoice
    self.pay_onchain_dialog(self.get_coins(), invoice.outputs)
  File "/usr/lib/python3/dist-packages/electrum/gui/qt/main_window.py", line 1668, in pay_onchain_dialog
    if not d.have_enough_funds_assuming_zero_fees():
  File "/usr/lib/python3/dist-packages/electrum/gui/qt/confirm_tx_dialog.py", line 116, in have_enough_funds_assuming_zero_fees
    tx = self.make_tx(0)
  File "/usr/lib/python3/dist-packages/electrum/gui/qt/main_window.py", line 1653, in <lambda>
    make_tx = lambda fee_est: self.wallet.make_unsigned_transaction(
  File "/usr/lib/python3/dist-packages/electrum/wallet.py", line 1273, in make_unsigned_transaction
    tx.locktime = get_locktime_for_new_transaction(self.network)
  File "/usr/lib/python3/dist-packages/electrum/wallet.py", line 209, in get_locktime_for_new_transaction
    if chain.is_tip_stale():
  File "/usr/lib/python3/dist-packages/electrum/blockchain.py", line 490, in is_tip_stale
    header = self.header_at_tip()
  File "/usr/lib/python3/dist-packages/electrum/blockchain.py", line 486, in header_at_tip
    return self.read_header(height)
  File "/usr/lib/python3/dist-packages/electrum/blockchain.py", line 201, in func_wrapper
    return func(self, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/electrum/blockchain.py", line 478, in read_header
    raise Exception('Expected to read a full header. This was only {} bytes'.format(len(h)))