refactor: improve error handling in shutdown_chrome function

[Aermberry]

I made some adjustments based on the following errors for Chrome Version 147.0.7727.117 (Official Build) (64-bit)：

uv run main.py
Traceback (most recent call last):
  File "E:\Home\desktop\enable-chrome-ai\main.py", line 159, in <module>
    main()
    ~~~~^^
  File "E:\Home\desktop\enable-chrome-ai\main.py", line 137, in main
    terminated_chromes = shutdown_chrome()
  File "E:\Home\desktop\enable-chrome-ai\main.py", line 54, in shutdown_chrome
    elif process.parent() is not None and process.parent().name() == process.name():
                                          ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'name'