Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/__init__.py", line 1705, in __call__
    return self.func(*args)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/multicall.py", line 176, in handler
    r = l[i](event)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/filelist.py", line 54, in close_all_callback
    reply = edit.close()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/pyshell.py", line 1014, in close
    return EditorWindow.close(self)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/editor.py", line 1015, in close
    reply = self.maybesave()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/outwin.py", line 93, in maybesave
    return 'yes' if self.get_saved() else 'no'
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/idlelib/editor.py", line 948, in get_saved
    return self.undo.get_saved()
AttributeError: 'NoneType' object has no attribute 'get_saved'