Index: /trunk/src/org/openstreetmap/josm/gui/help/HelpUtil.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/help/HelpUtil.java	(revision 8638)
+++ /trunk/src/org/openstreetmap/josm/gui/help/HelpUtil.java	(revision 8639)
@@ -99,5 +99,5 @@
      */
     public static String extractAbsoluteHelpTopic(String url) {
-        if (!url.startsWith(getWikiBaseHelpUrl())) return null;
+        if (url == null || !url.startsWith(getWikiBaseHelpUrl())) return null;
         url = url.substring(getWikiBaseHelpUrl().length());
         String prefix = getHelpTopicPrefix(LocaleType.ENGLISH);