VisitTime.getVisitInformationPerServerTime: Empty hours are not returned #2363

When you request the VisitTime.getVisitInformationPerServerTime for a date having no visit, it doesn't return 0 but an empty array.

I think the API should return the 0 value for every past date when there is no visit. The empty response should be reserved for future dates (that doesn't exist). So the response is predictable.

(In [4583]) Fixes #2363