Fix filter days before and after issue

[roelVerdonschot]

#216

When using the before and after filter events inside the range were removed, I had to update 1 line and add an extra check (parentheses) to make it work.

I changed this line in removeLastEventIfOutsideWindowAndNonRecurring()

• if (!isset($lastEvent['RRULE']) || $lastEvent['RRULE'] === '' && $this->doesEventStartOutsideWindow($lastEvent)) {

to

• if ((!isset($lastEvent['RRULE']) || $lastEvent['RRULE'] === '') && $this->doesEventStartOutsideWindow($lastEvent)) {

and had to add this if to the $events foreach in reduceEventsToMinMaxRange()

if ($anEvent === null) {
    unset($events[$key]);
    continue;
}

I'm using v2.1.11