File "electrum/gui/qt/main_window.py", line 3234, in closeEvent
  File "electrum/gui/qt/main_window.py", line 3255, in clean_up
  File "electrum/gui/qt/__init__.py", line 301, in close_window
  File "electrum/daemon.py", line 286, in stop_wallet
  File "electrum/address_synchronizer.py", line 169, in stop_threads
  File "electrum/util.py", line 356, in <lambda>
  File "electrum/util.py", line 352, in do_profile
  File "electrum/storage.py", line 88, in write
  File "electrum/storage.py", line 104, in _write