Emms Browse in terminal complains about needing the window system when thumbnails are enabled

[Nathan R. DeGruchy]

Hello,

For a while now, I've been using Emacs in the GUI frame mode, but I've recently 
taken to using Emacs in the terminal. When I call emms-smart-browse from a 
terminal session, and I try to expand an album in my library, Emacs complains 
about needing the window system. Now, I know that displaying images in the 
terminal is off the table, but it's odd there isn't some guard against this in 
practice.

Anyway, I was able to work around it by not specifying emms-browser-covers 
unless Emacs is using a window system. ala:

(when (window-system)
  (setq emms-browse-covers 'emms-browser-cache-thumbnail-async))

https://git.degruchy.link/ndegruchy/Emacs/src/branch/main/settings.d/required-packages.el#L117-L139

yrk on #emacs said I should write in and report it as a bug.

Thanks!