bug5876: support TrackedRace.getCourseAreaId() based on race logs attached

java/com.sap.sailing.domain.shared.android/src/com/sap/sailing/domain/base/SharedDomainFactory.java

@@ -102,6 +102,7 @@ public interface SharedDomainFactory<RLR extends RaceLogResolver> extends Compet
     
     /**
      * Gets the {@link CourseArea} with passed id; if there is no such {@link CourseArea} <code>null</code> will be returned.
+     * This also applies when {@code null} is being passed as the {@code courseAreaId}.
      */
     CourseArea getExistingCourseAreaById(Serializable courseAreaId);
     

java/com.sap.sailing.domain.shared.android/src/com/sap/sailing/domain/base/impl/SharedDomainFactoryImpl.java

@@ -380,7 +380,7 @@ public class SharedDomainFactoryImpl<RLR extends RaceLogResolver> implements Sha
 
     @Override
     public CourseArea getExistingCourseAreaById(Serializable courseAreaId) {
-        return courseAreaCache.get(courseAreaId);
+        return courseAreaId == null ? null : courseAreaCache.get(courseAreaId);
     }
 
     @Override