Fix for undefined method + for nil class error

Signed-off-by: Vasu1105 <vasundhara.jagdale@chef.io>

lib/inspec/profile_context.rb

@@ -91,7 +91,7 @@ module Inspec
     end
 
     def all_controls
-      ret = @rules.values
+      ret = @rules.values.reject(&:nil?)
       ret += @control_subcontexts.map(&:all_rules).flatten
       ret
     end