We upgrade from 1.504 to 1.510 and can no longer login.

The default URL gives us:

java.lang.NullPointerException
at com.thoughtworks.xstream.converters.ConversionException.add(ConversionException.java:65)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1066)
at hudson.util.XStream2.unmarshal(XStream2.java:109)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045)
at hudson.XmlFile.unmarshal(XmlFile.java:166)
at hudson.Plugin.load(Plugin.java:239)
at hudson.plugins.global_build_stats.GlobalBuildStatsPlugin.load(GlobalBuildStatsPlugin.java:98)
at hudson.plugins.global_build_stats.business.GlobalBuildStatsPluginSaver.reloadPlugin(GlobalBuildStatsPluginSaver.java:98)
at hudson.plugins.global_build_stats.business.GlobalBuildStatsBusiness.reloadPlugin(GlobalBuildStatsBusiness.java:382)
at hudson.plugins.global_build_stats.GlobalBuildStatsPlugin$GlobalBuildStatsItemListener.onLoaded(GlobalBuildStatsPlugin.java:149)
at jenkins.model.Jenkins.<init>(Jenkins.java:850)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.model.Hudson.<init>(Hudson.java:77)
at hudson.WebAppMain$2.run(WebAppMain.java:214)