OnlineMapsControlBaseUI is the base class for OnlineMapsUIImageControl and OnlineMapsUIRawImageControl.
EventSystem is a mandatory part of uGUI, without which interaction with UI will not work.
So what's the point of disabling EventSystem?

We added this check, and in the next version HitTest will return false if EventSystem.current == null.

We have a case where we disabled the EventSystem.current with :
EventSystem.current.enabled = false;

And this create a null reference on the EventSystem.current in your script cause there is a missing check to avoid this.

Line 132, I replace :
EventSystem.current.RaycastAll(pe, hits);

with :
if (EventSystem.current != null)
    EventSystem.current.RaycastAll(pe, hits);