Website generation NPE

website:
[exec] ./content/architecture.textile -> ./output/architecture.textile
[exec] ./content/development.textile -> ./output/development.textile
[exec] ./content/docs.textile -> ./output/docs.textile
[exec] ./content/download.textile -> ./output/download.textile
[exec] ./content/eclipse.png -> ./output/eclipse.png
[exec] ./content/eclipse_feature.png -> ./output/eclipse_feature.png
[exec] ./content/eclipse_install.png -> ./output/eclipse_install.png
[exec] ./content/getting-started.textile -> ./output/getting-started.textile
[exec] ./content/how-to-contribute.textile -> ./output/how-to-contribute.textile
[exec] ./content/how-to-use-with-jmock.textile -> ./output/how-to-use-with-jmock.textile
[exec] ./content/idea.png -> ./output/idea.png
[exec] ./content/idea_plugins.png -> ./output/idea_plugins.png
[exec] ./content/index.textile -> ./output/index.textile
[exec] ./content/jbehave.css -> ./output/jbehave.css
[exec] ./content/license.textile -> ./output/license.textile
[exec] ./content/logo.gif -> ./output/logo.gif
[exec] ./content/mailing-lists.textile -> ./output/mailing-lists.textile
[exec] ./content/minimock.textile -> ./output/minimock.textile
[exec] skinner.rb:122:in `add_class': undefined method `attributes' for nil:NilClass (NoMethodError)
[exec] from skinner.rb:113:in `skin_content_file'
[exec] from skinner.rb:87:in `skin_content'
[exec] from skinner.rb:82:in `each'
[exec] from skinner.rb:82:in `skin_content'
[exec] from skinner.rb:136:in `build_site'
[exec] from skinner.rb:141
[exec] Result: 1
[copy] Copying 18 files to /Users/cv/src/jbehave/delete_me/1.0-SNAPSHOT/website