try better handling of corrupt blobs

@developer: please revert if I'm wrong
see http://forum.yacy-websuche.de/viewtopic.php?f=8&t=3334

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7872 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/net/yacy/kelondro/rwi/ReferenceIterator.java

@@ -61,6 +61,7 @@ public class ReferenceIterator <ReferenceType extends Reference> extends LookAhe
         Map.Entry<byte[], byte[]> entry;
         while (this.blobs.hasNext()) {
             entry = this.blobs.next();
+            if (entry == null) break;
             try {
                 row = RowSet.importRowSet(entry.getValue(), this.factory.getRow());
                 if (row == null) {