是什么导致我的“未定义方法`[]'为nil：NilClass”错误？

Exception:

例外：

NoMethodError in CsdashboardController#index

undefined method `[]' for nil:NilClass
Rails.root: /opt/csdashboard

Application Trace | Framework Trace | Full Trace
app/controllers/csdashboard_controller.rb:106:in `index'
Request

Parameters:
None
NoMethodError in Csdashboard