This checks that a server config section is not empty when saving.
Note that I don't have any any sections in my server config which are currently empty, but if that is valid (ie. a section [header] is allowed with no settings under it), this should be modified or not accepted.
I did see one empty [jailkit] section get saved in datalog records, do to other bug(s)/issue(s), and it came to mind that this could easily be prevented. I don't know exactly how that other issue happened though so I can't test it in a live "bug scenario".
