update changelog for HUDSON-8391

changelog.html

@@ -44,6 +44,8 @@ Upcoming changes</a>
    Added CharacterEncodingFilter to prevent Non-ASCII characters from getting garbled.
   <li class=bug> Maven mirrors not used when project uses Maven 2.2
    (<a href="http://issues.hudson-ci.org/browse/HUDSON-8387">issue 8387</a>) 
+  <li class=bug> NPE while parsing POMs
+   (<a href="http://issues.hudson-ci.org/browse/HUDSON-8391">issue 8391</a>)   
 </ul>
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