Cannot update diary on the front end

[kazweda]

ℹ️ https://realpython.com/django-diary-project-python/

Describe the bug
On step5, a error occured while I tried to update a diary on the front end.

To Reproduce

1. Display a diary.

http://127.0.0.1:8000/entry/1

2. Then move to update form

http://127.0.0.1:8000/entry/1/update

3. Edit content and click "save".

4. Then I got this error.

Screenshots
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