Fix null handling in getSunTransit(Date,Date) (#243)

Author: dickermoshe

src/main/java/com/kosherjava/zmanim/AstronomicalCalendar.java

@@ -598,6 +598,9 @@ public Date getSolarMidnight() {
 	 */
 	public Date getSunTransit(Date startOfDay, Date endOfDay) {
 		long temporalHour = getTemporalHour(startOfDay, endOfDay);
+		if (temporalHour == Long.MIN_VALUE) {
+			return null;
+		}
 		return getTimeOffset(startOfDay, temporalHour * 6);
 	}