*******FIXED******
For anyone wondering or reading this I have managed to fix this. I got this error because I clicked "update" on the modules page and then my modules manager section of BO crashed.
I renamed /modules/ps_facetedsearch to something random like "ps_facetedsearchOLD" and re-uploaded this file via FTP:
Quote
Once uploaded faceted search should show up in your modules list again but requiring an update. Click "update" (I know risky right lol) and this time it should complete successfully. Voila! All fixed 