Fixing minifiers when file has no extension

The following error would occur on Ruby 1.9.3 + awestruct 0.5.5:

An error occurred: can't convert nil into String
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/page.rb:167:in `digest'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/page.rb:167:in `hexdigest'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/page.rb:167:in `rendered_content'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/engine.rb:285:in `generate_page'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/engine.rb:273:in `block in generate_output'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/engine.rb:270:in `each'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/engine.rb:270:in `generate_output'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/engine.rb:79:in `run'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/cli/generate.rb:21:in `run'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/cli/invoker.rb:125:in `invoke_generate'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/lib/awestruct/cli/invoker.rb:49:in `invoke!'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/gems/awestruct-0.5.5/bin/awestruct:9:in `<top (required)>'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/bin/awestruct:23:in `load'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/bin/awestruct:23:in `<main>'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/bin/ruby_executable_hooks:15:in `eval'
/Users/xcoulon/.rvm/gems/ruby-1.9.3-p484@jbosstools-website/bin/ruby_executable_hooks:15:in `<main>'