我正在将我的应用程序部署到生产中（好吧，至少尝试）。我一直遇到这个错误：
/opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/wicked_pdf-0.11.0/lib/wicked_pdf/railtie.rb:6:in `<top (required)>': uninitialized constant Rails::VERSION (NameError)
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/wicked_pdf-0.11.0/lib/wicked_pdf.rb:27:in `require'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/wicked_pdf-0.11.0/lib/wicked_pdf.rb:27:in `<top (required)>'
from /opt/www/sunstar/releases/20150325005143/config/application.rb:2:in `require'
from /opt/www/sunstar/releases/20150325005143/config/application.rb:2:in `<top (required)>'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:141:in `require'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:141:in `require_application_and_environment!'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:67:in `console'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /opt/www/sunstar/shared/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands.rb:17:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
任何人都有此错误的经验吗？我使用的是铁路4.2.0，我看到4.2.1已经出来但不确定我是否应该更新或回滚。