Fix tests
Fix tests

When there aren't many incidents, such as with dummy data, avoid
a NULL being passed back to the stats endpoint.

linkedin/iris,dwang159/iris-api,jrgp/iris-api-opensource,linkedin/iris,dwang159/iris-api,linkedin/iris,jrgp/iris-api-opensource,jrgp/iris-api-opensource,dwang159/iris-api,houqp/iris-api,linkedin/iris,dwang159/iris-api,jrgp/iris-api-opensource,houqp/iris-api