IndexError: list index out of range when trying to install Plus! themes

Hello there!

so I keep getting this error whenever I attempt to install a Plus! theme. I have even tried using the _Friends_ theme that was showcased in the Readme to see whether the themes I downloaded were the problem, but that doesn't appear to be the error; since the error also occurs when I attempt to use this theme. Here's a Pastebin with the `.log` file: https://pastebin.com/v6YUGjZ8

I'm running on Manjaro Linux with XFCE 4.14 and I've tried both the GUI and the CLI version, but neither works.

Anyone have an idea what I may be doing wrong? I'd appreciate it!