Redis::collectHistograms() throws PHP warning: sort() expects parameter 1 to be array, boolean given

[cweiske]

When no histogram data have been pushed into redis yet, calling Prometheus\Storage\Redis::collectHistograms results in a PHP warning:

warning: sort() expects parameter 1 to be array, boolean given

This is because

$keys = $this->redis->sMembers(self::$prefix . Histogram::TYPE . self::PROMETHEUS_METRIC_KEYS_SUFFIX);

returns false.

[cweiske]

Is there anything I can do to get this merged?

[ahoulgrave]

This is happening and a blocker for using this package.