fix for possible synchronization problem

see also: http://forum.yacy-websuche.de/viewtopic.php?f=6&t=2292&hilit=&p=16787#p16787

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@6234 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/kelondro/blob/ArrayStack.java

@@ -445,7 +445,7 @@ public class ArrayStack implements BLOB {
      * ask for the number of blob entries in each blob of the blob array
      * @return the number of entries in each blob
      */
-    public int[] sizes() {
+    public synchronized int[] sizes() {
         int[] s = new int[blobs.size()];
         int c = 0;
         for (blobItem bi: blobs) s[c++] = bi.blob.size();