What is the problem?

When the cursor is in one of the translation inputs and you click on something that navigates you away from the page (e.g. "Log in"), you see "An error occurred when fetching the preview...".

This seems to mainly affect Firefox.
These include:

• "Log in"
• "Log out"
• "pick another file"
• Some of the links in the footer

Steps to reproduce problem

1. Go to any file in SVGTranslate (e.g. https://tools.wmflabs.org/svgtranslate-test/File:2002_AJ129-orbit_(multilingual).svg )
2. Click in any of the translation inputs (select a translation language first if necessary)
3. Click "pick another file"

Expected behavior: Go to the SVGTranslate front page
Observed behavior: See a popup error (briefly) before going to the SVGTranslate front page

Proposed solution

In T221783, we disabled the "Download" link while a preview was being fetched. We could do the same for other links on the page.

Environment

Operating system: Debian Stretch
Browser: Firefox 60