fix(Scheduler): fix NPE on validationResult#lastCalendarDate

Author: landonreed

src/main/java/com/conveyal/datatools/common/utils/Scheduler.java

@@ -185,6 +185,7 @@ public static void scheduleExpirationNotifications (FeedSource feedSource) {
         if (
             latest != null &&
                 latest.validationResult != null &&
+                latest.validationResult.lastCalendarDate != null &&
                 latest.validationResult.lastCalendarDate.isAfter(LocalDate.now())
         ) {
             // get parent project