fix division by zero: set default sensible frequency
fix division by zero: set default sensible frequency

raintank/metrictank,raintank/metrictank,replay/metrictank,raintank/raintank-metric,raintank/raintank-metric,replay/metrictank,OOM-Killer/metrictank,raintank/metrictank,OOM-Killer/metrictank,OOM-Killer/metrictank,replay/metrictank,raintank/metrictank,raintank/raintank-metric,replay/metrictank