Merge pull request #10373 from janko-m/fix-store-accessor

Fix a bug in ActiveRecord::Store accessors

activerecord/lib/active_record/store.rb

@@ -37,8 +37,8 @@ module ActiveRecord
         Array(keys).flatten.each do |key|
           define_method("#{key}=") do |value|
             send("#{store_attribute}=", {}) unless send(store_attribute).is_a?(Hash)
-            send(store_attribute)[key] = value
             send("#{store_attribute}_will_change!")
+            send(store_attribute)[key] = value
           end
     
           define_method(key) do