$ gem --version
[/home/rohit/.rvm/gems/ruby-1.9.3-p125@qnrDashboard/specifications/net-ssh-2.5.2.gemspec] isn't a Gem::Specification (NilClass instead).
[/home/rohit/.rvm/gems/ruby-1.9.3-p125@qnrDashboard/specifications/net-sftp-2.0.5.gemspec] isn't a Gem::Specification (NilClass instead).
[/home/rohit/.rvm/gems/ruby-1.9.3-p125@qnrDashboard/specifications/net-ssh-gateway-1.1.0.gemspec] isn't a Gem::Specification (NilClass instead).
[/home/rohit/.rvm/gems/ruby-1.9.3-p125@qnrDashboard/specifications/net-scp-1.0.4.gemspec] isn't a Gem::Specification (NilClass instead).
使用 RVM 1.12.3、RubyGems 1.8.22 和 Ruby 1.9.3 版本。
为什么会出现这个错误?