function removeEvent(element, eventName, eventIndex) {
  if (element.__bunny_event_handlers !== undefined && element.__bunny_event_handlers.handlers[eventIndex] !== undefined) {
    element.removeEventListener(eventName, element.__bunny_event_handlers.handlers[eventIndex]);
    delete element.__bunny_event_handlers.handlers[eventIndex];
    // do not decrement counter, each new event handler should have next unique index
  }
  return null;
}
Remove event listener

@param {HTMLElement} element
@param {String} eventName
@param {Number} eventIndex

@returns {null}