Redmine

I installed redmine to a centos WHM vps server.
you can see the error at there http://redmine.labsera.com/

ruby -v
ruby 1.8.7 (2013-06-27 patchlevel 374) [i686-linux]

gem -v
1.8.25

uninitialized constant Redmine::Helpers::Gantt::IssueRelation (NameError)
/home/labsera/redmine/lib/redmine/helpers/gantt.rb:28
/home/labsera/redmine/lib/redmine.rb:51
/home/labsera/redmine/config/initializers/30-redmine.rb:4
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/engine.rb:593
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/engine.rb:592:in `each'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/engine.rb:592
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/initializable.rb:30:in `instance_exec'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/initializable.rb:30:in `run'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/initializable.rb:55:in `run_initializers'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/initializable.rb:54:in `each'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/initializable.rb:54:in `run_initializers'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/application.rb:136:in `initialize!'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/railtie/configurable.rb:30:in `send'
/usr/lib/ruby/gems/1.8/gems/railties-3.2.15/lib/rails/railtie/configurable.rb:30:in `method_missing'
/home/labsera/redmine/config/environment.rb:14
config.ru:3:in `require'
config.ru:3
/usr/lib/ruby/gems/1.8/gems/rack-1.4.5/lib/rack/builder.rb:51:in `instance_eval'
/usr/lib/ruby/gems/1.8/gems/rack-1.4.5/lib/rack/builder.rb:51:in `initialize'
config.ru:1:in `new'
config.ru:1