Cannot export theme

This has been a common issue I have noted by looking at reviews from the past 7 months. I went to install this extension today, and I found that every time I exported the file, it said that it couldn't install the extension, as the extension was corrupt. I can confirm it is, as there is a <600 byte blank SVG file, and a normal JSON file. I am surprised that this isn't being reported as much as it should. I looked through issues before reporting, but couldn't find any recent ones mentioning this, so I will say it here. This may be a duplicate, as this apparently has been an issue for 7 months or more.

I tried to include a screenshot, but the error message goes away before my system can get a screenshot (using F10: PRT SC/Print Screen)

Device specs

Browser version: Firefox Browser 87.0 for Ubuntu Linux 20.04.1
Operating system: Ubuntu Linux 20.04.1
DE: GNOME 3.36.1