Protection against NPE from getDataSourceID returning null

...java/src/org/sleuthkit/datamodel/AccountFileInstance.java

.../org/sleuthkit/datamodel/AggregateScoresChangedEvent.java

.../java/src/org/sleuthkit/datamodel/BlackboardArtifact.java

...java/src/org/sleuthkit/datamodel/BlackboardAttribute.java

...va/src/org/sleuthkit/datamodel/CommunicationsManager.java

bindings/java/src/org/sleuthkit/datamodel/ScoreChange.java

...ngs/java/src/org/sleuthkit/datamodel/TimelineManager.java