URLs with redundant slashes cause Unpoly to trigger a DOMException

[makmic]

Bug description

While testing an application which was using Unpoly, I noticed that the Cookie Banner was somehow not working at all.
The culprit however was the JavaScript exception within Unpoly's source code:

Uncaught DOMException: Failed to execute 'replaceState' on 'History': A history state object with URL 'http://en/sign-in' cannot be created in a document with origin 'http://foobar.lvh.me:3000' and URL 'http://foobar.lvh.me:3000//en/sign-in'.

Due to a copy&paste mistake I was accessing the page at http://foobar.lvh.me:3000//en/sign-in' (two forward slashes) instead of http://foobar.lvh.me:3000/en/sign-in'. That's a niche case, but as the application renders fine in this case I'd except Unpoly not to crash too.

Steps to reproduce the behavior:

1. Go to https://unpoly.com//install
2. See the following error in the console:

Uncaught DOMException: Failed to execute 'replaceState' on 'History': A history state object with URL 'https://install/' cannot be created in a document with origin 'https://unpoly.com' and URL 'https://unpoly.com//install'.

Browser version

• OS: Linux
• Browser Chrome
• Version 124

[adam12]

Thanks for the report. I see the same on Safari + MacOS.