Reorder conditions in HashWithIndifferentAccess#initialize

We should check the cheaper and more likely case first.

Author: byroot

activesupport/lib/active_support/hash_with_indifferent_access.rb

@@ -68,15 +68,15 @@ def nested_under_indifferent_access
     end
 
     def initialize(constructor = nil)
-      if constructor.respond_to?(:to_hash)
+      if constructor.nil?
+        super()
+      elsif constructor.respond_to?(:to_hash)
         super()
         update(constructor)
 
         hash = constructor.is_a?(Hash) ? constructor : constructor.to_hash
         self.default = hash.default if hash.default
         self.default_proc = hash.default_proc if hash.default_proc
-      elsif constructor.nil?
-        super()
       else
         super(constructor)
       end