我是ROR开发的新手。我正在尝试在服务器上部署ROR项目，但是当我尝试通过独角兽运行该应用程序时，该应用程序以以下错误结尾，但是在正常的开发服务器上，ROR应用程序可以正常工作。
I, [2019-03-13T17:43:41.807762 #4505] INFO -- : Refreshing Gem list
/var/lib/gems/2.5.0/gems/rack-2.0.6/lib/rack/session/abstract/id.rb:202:in `<class:Persisted>': uninitialized constant Rack::Session::Abstract::Persisted::RACK_SESSION (Na$ from /var/lib/gems/2.5.0/gems/rack-2.0.6/lib/rack/session/abstract/id.rb:200:in `<module:Abstract>'
from /var/lib/gems/2.5.0/gems/rack-2.0.6/lib/rack/session/abstract/id.rb:14:in `<module:Session>'
from /var/lib/gems/2.5.0/gems/rack-2.0.6/lib/rack/session/abstract/id.rb:12:in `<module:Rack>'
from /var/lib/gems/2.5.0/gems/rack-2.0.6/lib/rack/session/abstract/id.rb:10:in `<top (required)>'
from /var/lib/gems/2.5.0/gems/actionpack-5.1.6.1/lib/action_controller/metal/request_forgery_protection.rb:1:in `<top (required)>'
from /var/lib/gems/2.5.0/gems/actionpack-5.1.6.1/lib/action_controller/base.rb:225:in `<class:Base>'
from /var/lib/gems/2.5.0/gems/actionpack-5.1.6.1/lib/action_controller/base.rb:164:in `<module:ActionController>'
from /var/lib/gems/2.5.0/gems/actionpack-5.1.6.1/lib/action_controller/base.rb:5:in `<top (required)>'
from /var/lib/gems/2.5.0/gems/gritter-1.2.0/lib/gritter.rb:19:in `initialize'
from /var/lib/gems/2.5.0/gems/gritter-1.2.0/lib/gritter/railtie.rb:5:in `block in <class:Railtie>'
from /var/lib/gems/2.5.0/gems/railties-5.1.6.1/lib/rails/initializable.rb:30:in `instance_exec'
from /var/lib/gems/2.5.0/gems/railties-5.1.6.1/lib/rails/initializable.rb:30:in `run'
from /var/lib/gems/2.5.0/gems/railties-5.1.6.1/lib/rails/initializable.rb:59:in `block in run_initializers'
from /usr/lib/ruby/2.5.0/tsort.rb:228:in `block in tsort_each'
from /usr/lib/ruby/2.5.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /usr/lib/ruby/2.5.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /usr/lib/ruby/2.5.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /usr/lib/ruby/2.5.0/tsort.rb:347:in `each'
from /usr/lib/ruby/2.5.0/tsort.rb:347:in `call'
from /usr/lib/ruby/2.5.0/tsort.rb:347:in `each_strongly_connected_component'
from /usr/lib/ruby/2.5.0/tsort.rb:226:in `tsort_each'
from /usr/lib/ruby/2.5.0/tsort.rb:205:in `tsort_each'
from /var/lib/gems/2.5.0/gems/railties-5.1.6.1/lib/rails/initializable.rb:58:in `run_initializers'
from /var/lib/gems/2.5.0/gems/railties-5.1.6.1/lib/rails/application.rb:353:in `initialize!'
from /root/webapps/SchoolManagment/config/environment.rb:5:in `<top (required)>'
from config.ru:4:in `require_relative'
from config.ru:4:in `block in <main>'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:55:in `instance_eval'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:55:in `initialize'
from config.ru:1:in `new'
from config.ru:1:in `<main>'
from /var/lib/gems/2.5.0/gems/unicorn-5.5.0/lib/unicorn.rb:54:in `eval'
from /var/lib/gems/2.5.0/gems/unicorn-5.5.0/lib/unicorn.rb:54:in `block in builder'
from /var/lib/gems/2.5.0/gems/unicorn-5.5.0/lib/unicorn/http_server.rb:794:in `build_app!'
from /var/lib/gems/2.5.0/gems/unicorn-5.5.0/lib/unicorn/http_server.rb:141:in `start'
from /var/lib/gems/2.5.0/gems/unicorn-5.5.0/bin/unicorn:128:in `<top (required)>'
from /usr/local/bin/unicorn:23:in `load'