SysArchMeter: skip "n/a" values

Unavailable values are returned as "n/a" from lsb_release, skip these.

$ lsb_release -a
LSB Version:    1.4
Distributor ID: Arch
Description:    Arch Linux
Release:        rolling
Codename:       n/a

1 files changed, 5 insertions, 0 deletions

diff --git a/SysArchMeter.c b/SysArchMeter.c
index 083d079d..b4963c0a 100644
--- a/SysArchMeter.c
+++ b/SysArchMeter.c
@@ -38,6 +38,11 @@ static void SysArchMeter_updateValues(Meter* this, char* buffer, size_t size) {
                char* value = String_trim(&line[n + 1]);
                line[n] = '\0';
 
+               if(String_eq(value, "n/a")) {
+                  free(value);
+                  continue;
+               }
+
                if(String_eq(line, "Distributor ID"))
                   snprintf(distro[0], sizeof(distro[0]), "%s", value);
                else if(String_eq(line, "Release"))