Admin page History button has broken link for historical objects.

[ahmedaljawahiry]

Bug
When viewing a historical object in the admin, the "HISTORY" button on the top right does nothing on-click.

To Reproduce

1. Go to admin page.
2. Click on any model.
3. Click on an instance of the model to get to the admin form.
4. Click the "HISTORY" button in the top right.
5. Click on some past instance.
6. Click the "HISTORY" button in the top right again.
7. Nothing happens.

Expected behavior
On clicking the button, you return to the list of historical objects.

Screenshots
HTML from Chrome developer, showing an empty href:

Environment

• OS: Windows 10
• Browser (if applicable): Chrome
• Django Simple History Version: 2.7.0
• Django Version: 2.1.5
• Database Version: PostgreSQL 10.4

Additional context
I'm not 100% sure if this is coming from your side or mine. Every other piece of history-functionality appears to be working - I cant see what would cause this bug.

[rossmechanic]

Thanks for this @ahmed1293 ! I don't think that button ever worked. It's just there by default. You're more than welcome to submit a PR removing it or making it work. Thanks!

[ahmedaljawahiry]

Thanks for the response! Happy to help - will try to make time for this soon :)