fixed NPE that is probably caused by a change in the TracTrac system which for some races lists the race start time as null (probably used to be an empty string)

java/com.sap.sailing.gwt.ui/src/main/java/com/sap/sailing/gwt/ui/server/SailingServiceImpl.java

@@ -1048,7 +1048,7 @@ public class SailingServiceImpl extends ProxiedRemoteServiceServlet implements S
             result.add(new TracTracRaceRecordDTO(raceRecord.getID(), raceRecord.getEventName(), raceRecord.getName(),
                     raceRecord.getTrackingStartTime().asDate(), 
                     raceRecord
-                    .getTrackingEndTime().asDate(), raceRecord.getRaceStartTime().asDate(),
+                    .getTrackingEndTime().asDate(), raceRecord.getRaceStartTime() == null ? null : raceRecord.getRaceStartTime().asDate(),
                     raceRecord.getBoatClassNames(), raceRecord.getRaceStatus(), raceRecord.getRaceVisibility(), raceRecord.getJsonURL().toString(),
                     hasRememberedRegatta(raceRecord.getID())));
         }