Return all Event Types if no Event Type filter supplied

Instead of an empty array.
Line 51 checks to see whether the events parameter is an array, and if it isn't then it wraps it in an array. Line 50 sets events to null if no events were provided.

(If someone provides null as the events arguments then it becomes [null] on line 52, so I'll fix that)

Otherwise on line 59 events will either be an array or null, so there's no need to check if it's an array or not.

I will update the README and fix the above bug.