启动 rails 服务器时出错：code&.downcase AND region&.upcase

问：

我正在做一个Ruby on Rails项目。我已经设置好了一切，但是当我尝试通过执行“rails s”来启动服务器时，出现以下错误：

/home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser/browser.rb:9:in `require_relative': /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser/accept_language.rb:37: syntax error, unexpected '.' (SyntaxError)
        code&.downcase
              ^
/home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser/accept_language.rb:44: syntax error, unexpected '.'
        region&.upcase
                ^
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser/browser.rb:9:in `<top (required)>'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser.rb:3:in `require_relative'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/browser-5.1.0/lib/browser.rb:3:in `<top (required)>'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:81:in `require'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:81:in `block (2 levels) in require'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:76:in `each'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:76:in `block in require'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:65:in `each'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler/runtime.rb:65:in `require'
    from /usr/share/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/bundler.rb:114:in `require'
    from /home/syed/Desktop/offerletter/config/application.rb:9:in `<top (required)>'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands/commands_tasks.rb:78:in `require'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands/commands_tasks.rb:78:in `block in server'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands/commands_tasks.rb:75:in `tap'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands/commands_tasks.rb:75:in `server'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /home/syed/Desktop/offerletter/vendor/bundle/ruby/2.2.0/gems/railties-4.2.2/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

我尝试过的事情：

1. 捆绑安装
2. 捆绑包更新

1.Ubuntu 版本 - 20.4 LTS

2.rails - 4.2.2 （由于各种原因不得不维护此版本）

3.ruby - 2.2.2 （由于各种原因不得不维护这个版本）

注意：如果您需要我提供任何进一步的信息来解决问题，请在评论部分询问。

请帮忙。