Fix: do not write data if the perfdata string is just void. npcd will just drop it. Fix #1
Fix: do not write data if the perfdata string is just void. npcd will just drop it. Fix #1

shinken-monitoring/mod-npcdmod,kaji-project/shinken-mod-npcdmod,shinken-monitoring/mod-npcdmod,staute/shinken-mod-npcdmod,staute/shinken-mod-npcdmod,kaji-project/shinken-mod-npcdmod