Index: src/java/org/apache/nutch/metadata/Metadata.java
===================================================================
--- src/java/org/apache/nutch/metadata/Metadata.java	(revision 478610)
+++ src/java/org/apache/nutch/metadata/Metadata.java	(working copy)
@@ -209,6 +209,10 @@
     for (int i = 0; i < names.length; i++) {
       Text.writeString(out, names[i]);
       values = getValues(names[i]);
+      if (values.length > 0 && values[0] == null) {
+        out.writeInt(0);
+        continue;
+      }
       out.writeInt(values.length);
       for (int j = 0; j < values.length; j++) {
         Text.writeString(out, values[j]);