fix for npe

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7379 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/server/serverObjects.java

@@ -237,7 +237,7 @@ public class serverObjects extends HashMap<String, String> implements Cloneable
      * @see #putNum(String, long)
      */
     public String putNum(final String key, final String value) {
-        return this.put(key, Formatter.number(value));
+        return this.put(key, value == null ? "" : Formatter.number(value));
     }