Sorry for being silent so long, I couldn’t reply earlier.
It looks like the issue is due to some missing dependency for image handling in GTK. I did some research, but I couldn’t understand what an “image loader” exactly is in GTK jargon, only that it is related to image decoding. I instaled glycine-related packages, to no avail.
However, the version of Tor Browser downloaded from the Tor Project’s website works well. Thus, I suppose the issue is introduced by the Manjaro package: I recommend you get in touch with whoever maintains it.