If an HTML file is added to a model's files, then you open it in the web interface, the UI recurses itself 3 times

[rmohns]

Describe the bug This is really best illustrated by screenshot:

I ran into this because I save documentation both as PDFs and also as SingleFile web archives.

To Reproduce Steps to reproduce the behavior:

1. Go to any model and upload an HTML file
2. Save the model, then click the blue "Open" button
3. You'll see the site iframed into itself three times. (Happy, something made it stop recursing.)

Expected behavior Opening an HTML file ought to just view it in place. Downloading would be an acceptable fallback.

Screenshots

Desktop (please complete the following information):

• OS: MacOS
• Browser: Safari, Firefox

Smartphone (please complete the following information):

• n/a (not tested)

Additional context I also ran into a related problem with downloading an HTML file (spoiler: it doesn't work). I'll open a separate issue for that.

[Floppy]

You've got to admit it's kind of pretty though 😁

Duplicate of #3662 , but I'll leave this open to remind me to look at it properly.