move destroy logic into library method & transaction

app/controllers/custom_wizard/admin/wizard.rb

@@ -26,8 +26,6 @@ class CustomWizard::AdminWizardController < CustomWizard::AdminController
 
   def remove
     if CustomWizard::Template.remove(@wizard.id)
-      related_custom_fields = CategoryCustomField.where(name: 'create_topic_wizard', value: @wizard.name)
-      related_custom_fields.destroy_all
       render json: success_json
     else
       render json: failed_json

lib/custom_wizard/template.rb

@@ -64,6 +64,8 @@ class CustomWizard::Template
       ensure_wizard_upload_references!(wizard_id)
       PluginStore.remove(CustomWizard::PLUGIN_NAME, wizard.id)
       clear_user_wizard_redirect(wizard_id, after_time: !!wizard.after_time)
+      related_custom_fields = CategoryCustomField.where(name: 'create_topic_wizard', value: wizard.name)
+      related_custom_fields.destroy_all
     end
 
     clear_cache_keys