Fix dcm4che#2012 : List Retrieve Tasks as CSV fails if batch ID is nu…

…ll and status is TO SCHEDULE

dcm4chee-arc-entity/src/main/java/org/dcm4chee/arc/entity/RetrieveTask.java

@@ -417,7 +417,9 @@ public void writeAsCSVTo(Writer writer, char delimiter) throws IOException {
             writer.append(delimiter).write(queueName);
             writer.append(delimiter).write(deviceName);
             writer.append(delimiter).write("TO SCHEDULE");
-            writer.append(delimiter).append(delimiter).write(batchID);
+            writer.append(delimiter).append(delimiter);
+            if (batchID != null)
+                writer.write(batchID);
             writer.append(delimiter).append(delimiter).append(delimiter).append(delimiter).append(delimiter);
         } else
             queueMessage.writeStatusAsCSVTo(writer, df, delimiter);