WP_Error could not be converted to string

Could you inspect that file and see if it’s legit?
I don’t have that file..

Here are the contents of that file: https://pastebin.com/zaN4p3GV

I probably was looking at an old version of the theme. The code you pasted seems legit to me.
I’d not spend too much time, but put a @ in front of str_replace on that line, as well as for the line after. But that’s me having tons of other stuff to do ??