Comment # 9 on bug 948729 from Ancor Gonzalez Sosa

Something that could be done is detecting if the selected file
(/var/log/messages by default) is empty or not present. In that case, show a
pop-up with a message similar to this (needs rephrasing).

"There is no content in the selected log file (%s). Choose another one.
Take into account that the activity of the main components of the system is now
logged to the systemd journal. You can inspect the systemd journal in a
convenient way using the YaST journal module."

I think that's a sensible solution, better than doing nothing but not too
disruptive.