Skip over outputting in a graphite metric when the args is empty
Skip over outputting in a graphite metric when the args is empty

This fixes issues specifically in graphite metrics where sensu will
append an extra '\n' to the metrics it sends to graphite and will cause
errors on the graphite relays like:
"[listener] invalid line () received from client 127.0.0.1:44116,
ignoring"

for graphite metrics when we call the OK status check (which should be
default for metrics as they don't get handled/alerted onthe sensu side)

sensu-plugins/sensu-plugin,zbintliff/sensu-plugin