Skip snapshot remark_value if the key does not given

lib/shotengai/controller/merchant/product_snapshots_controller.rb

@@ -30,10 +30,12 @@ module Shotengai
         
         private
           def resource_params
-            remark_value = params.require(resource_key).fetch(:remark_value, {}).permit!
+            remark_value = params.require(resource_key).fetch(:remark_value, nil)&.permit!
             params.require(resource_key).permit(
               :revised_amount
-            ).merge(remark_value: remark_value)
+              # WARNING: if .fetch(:remark_value, {}) get value {}
+              #   it would update to this value
+            ).merge(remark_value: remark_value || @resource.remark_value)
           end
 
           def rewrite_params