the library tables are text files that hold the information where the real libs are located (see Library management in KiCad version 5 for details)
The fact that KiCad thinks you are under 16.04 might mean you installed KiCad from the wrong source. Could be either you entered the wrong repo or there is something wrongly setup with your package manager. I suspect that KiCad compiled for 16.04 might expect different dependencies than you have on 18.04 which could explain the crash. If that is the case then the library tables might not have anything to do with what you see.
I have too little experience with apt (the package manager) to be of help here as I use a dnf (successor to yum) based linux distro.