/usr/lib/ruby/1.8/rexml/text.rb:291:in `normalize': private method `gsub' called for 0:Fixnum (NoMethodError)
        from /usr/lib/ruby/1.8/rexml/element.rb:1124:in `[]='
        from /usr/lib/ruby/1.8/rexml/element.rb:586:in `add_attribute'
        from /usr/lib/ruby/site_ruby/1.8/booh/booh-lib.rb:320:in `gen_thumbnails'
        from /usr/lib/ruby/site_ruby/1.8/booh/booh-lib.rb:284:in `gen_thumbnails_element'
        from /usr/bin/booh-backend:818:in `walk_source_dir'
        from /usr/bin/booh-backend:813:in `each'
        from /usr/bin/booh-backend:813:in `walk_source_dir'
        from /usr/bin/booh-backend:657:in `each'
        from /usr/bin/booh-backend:657:in `walk_source_dir'
        from /usr/bin/booh-backend:1278