Fix editing about spec_rewrite

lib/shotengai/controller/merchant/product_snapshots_controller.rb

@@ -22,8 +22,8 @@ module Shotengai
         def update
           @resource.class.transaction do
             @resource.attributes = resource_params
-            @resource.has_changes_to_save? && edit_only_unpaid
-            @resource.update_columns(rewrite_params.to_h) # skip validation
+            @resource.has_changes_to_save? && edit_only_unpaid && @resource.save!
+            @resource.update_columns(rewrite_params.to_h) if rewrite_params.present? # skip validation
           end
           head 200
         end
@@ -41,7 +41,7 @@ module Shotengai
           end
 
           def edit_only_unpaid
-            raise Shotengai::WebError.new('订单已支付，不可修改该快照。', '-1', 403) unless @resource.order.unpaid?
+            @resource.order.unpaid? || raise(Shotengai::WebError.new('订单已支付，不可修改该快照。', '-1', 403))
           end
 
           def manager_auth