BUG/MINOR: log: fix memory error handling in parse_logsrv()

BUG/MINOR: log: fix memory error handling in parse_logsrv()

A check was missing in parse_logsrv() to make sure that malloc-dependent
variable is checked for non-NULL before using it.

If malloc fails, the function raises an error and stops, like it's already
done at a few other places within the function.

This partially fixes GH #2130.

It should be backported to every stable versions.