File "electrum/gui/qt/main_window.py", line 3171, in closeEvent
  File "electrum/gui/qt/main_window.py", line 3192, in clean_up
  File "electrum/gui/qt/__init__.py", line 286, in close_window
  File "electrum/daemon.py", line 276, in stop_wallet
  File "electrum/address_synchronizer.py", line 172, in stop_threads
  File "electrum/util.py", line 367, in <lambda>
  File "electrum/util.py", line 363, in do_profile
  File "electrum/storage.py", line 122, in write
  File "electrum/storage.py", line 139, in _write