bug4651: added null safety for search in case leaderboard groups belong to no event

Change-Id: Ia8b7705610928e1a58b11cdf9a15c33b41d0efe6

java/com.sap.sailing.server/src/com/sap/sailing/server/impl/RegattaByKeywordSearchService.java

@@ -126,12 +126,12 @@ public class RegattaByKeywordSearchService {
      * 
      * @param leaderboard the leaderboard to get the matching events for
      * @param leaderboardGroup the LeaderboardGroup hosting the leaderboard
-     * @param events all events hosting the LeaderboardGroup
+     * @param events all events hosting the LeaderboardGroup; may be {@code null}; if {@code null}, result will be {@code null}
      * @return the best matching events for the given Leaderboard/LeaderboardGroup
      */
     private Set<Event> filterEventsForLeaderboard(Leaderboard leaderboard, LeaderboardGroup leaderboardGroup, Set<Event> events) {
         final Set<Event> result;
-        if (leaderboardGroup.hasOverallLeaderboard()) {
+        if (events != null && leaderboardGroup.hasOverallLeaderboard()) {
             CourseArea defaultCourseArea = leaderboard.getDefaultCourseArea();
             Set<Event> preResult = null;
             if (defaultCourseArea != null) {