zero does not work when eventObj is null

[genru]

Hi,

thanks for your great job. I just tried to clean all event counter but it seems does not work. I wrote some code to reproduce this issue hope it helps.

zero specified event(zero({eventObj: '123456'}) in my case) works perfectly

"redis-metrics": "^2.0.0"

...
const hitCounter = metrics.counter('anchorQueryHit', { timeGranularity: 'day' });
...
    describe.only('#zero', () => {
        it('should clean all', function(done) {
            hitCounter.incr({eventObj:'123456'}).then((data) => {
                return hitCounter.count({eventObj: '123456'})
            }).then(count => {
                // count.should.equal(1);
                return hitCounter.zero();          // <--- expect all counter cleaned, include '123456's
            }).then(() => {
                return hitCounter.count({eventObj: '123456'});
            }).then(count => {
                count.should.equal(0);            // <--- no, it does not
                done();
            }).catch(done)
        })
    })