[Doitsu]

I'm working on a Windows-only plugin that'll crash Sigil, if the click Plugin Runner window close button (X) is clicked while the plugin is running. (On my Linux machine, Sigil displays: Error Parsing Result XML: Encountered incorrectly encoded content., but it doesn't crash.)

Steps to reproduce this issue:

1. Install and run the crash plugin.
2. Click the first option in the list box.
3. Click the Plugin Runner window close button (X).

The plugin uses the following code:

Spoiler:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys
from tkinter import Tk,  Listbox
       
def run(bk):

    # list box helper function
    def get_list(event):
        index = Lb1.curselection()[0]
        selected_option = Lb1.get(index)
        print('You selected:', selected_option, '\n')

    # define list box
    options = ['option 1', 'option 2', 'option 3']
    root = Tk()
    Lb1 = Listbox(root)
    Lb1.config(width=0, height=0)
    Lb1.bind('<ButtonRelease-1>', get_list)
    
    # populate list box
    position = 0
    for option in options:
        position += 1
        Lb1.insert(position, option)
    Lb1.pack()
    root.mainloop()

    return 0
        
def main():
    print('I reached main when I should not have\n')
    return -1

if __name__ == "__main__":
    sys.exit(main())

How do I need to change the code to gracefully exit the plugin, if the Plugin Runner window is closed?