[rules-users] NPE in SlidingTimeWindow$SlidingTimeWindowComparator

I'm getting a null pointer exception on either line 232 or 233 of SlidingTimeWindow. The only window I'm using is: rule "Mark up to date" timer(int: 5m) when $store: Store() exists (SensorReading (this.store == $store) over window:time(5m)) then ... end The rule never fires; this happens when the sliding time window is expiring tuples. It appears the comparator needs to handle nulls, but there's nothing in the JavaDocs about that.