fix for http://www.yacy-forum.de/viewtopic.php?p=18610#18610

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@1841 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/plasma/plasmaCrawlBalancer.java

@@ -91,8 +91,10 @@ public class plasmaCrawlBalancer {
     
     private int sizeDomainStacks() {
         int sum = 0;
+        if (domainStacks != null) synchronized (domainStacks) {
             Iterator i = domainStacks.values().iterator();
             while (i.hasNext()) sum += ((ArrayList) i.next()).size();
+        }
         return sum;
     }