SQOOP-879: NPE when deleting job object that do not have associated any submissions

(Jarcec Cecho via Cheolsoo Park)

repository/repository-derby/src/main/java/org/apache/sqoop/repository/derby/DerbyRepositoryHandler.java

@@ -727,6 +727,11 @@ public boolean existsJob(long id, Connection conn) {
   public boolean inUseJob(long jobId, Connection conn) {
     MSubmission submission = findSubmissionLastForJob(jobId, conn);
 
+    // We have no submissions and thus job can't be in use
+    if(submission == null) {
+      return false;
+    }
+
     // We can't remove running job
     if(submission.getStatus().isRunning()) {
       return true;