[syslog-ng] Value is dropped or unset in resolved destination template

[Fabien Wernli]

Hi Mark,

It's really hard to tell what's happening without seeing your full
configuration. Remember messages can go through multiple logpaths, some of
which the variables are probably empty in.

That being said, if I were you I'd use a default value for your macros in any
case, much safer e.g.:

    destination d_default {
            file("`BASEPATH`/${location:-hidden}/$(lowercase ${HOST})/${app:-unknown}/$(lowercase ${HOST})_${app:-unknown}.log"
            create_dirs(yes)
            flags("threaded", "no-multi-line"));
    };