Enforce case requires else; allow else nil

Author: bf4

.rubocop.yml

@@ -45,6 +45,13 @@ Style/ClassAndModuleChildren:
 Style/Documentation:
   Enabled: false
 
+Style/MissingElse:
+  Enabled: true
+  EnforcedStyle: case
+
+Style/EmptyElse:
+  EnforcedStyle: empty
+
 Style/MultilineOperationIndentation:
   EnforcedStyle: indented
 

lib/active_model/serializer/include_tree.rb

@@ -68,6 +68,8 @@ def [](key)
           self.class.new(@hash[:*])
         when @hash.key?(:**)
           self.class.new(:** => {})
+        else
+          nil
         end
       end
     end