Use `includes(:priorities)` on Projects::LabelsController

app/controllers/projects/labels_controller.rb

@@ -126,7 +126,7 @@ def label
   alias_method :subscribable_resource, :label
 
   def find_labels
-    @available_labels ||= LabelsFinder.new(current_user, project_id: @project.id).execute
+    @available_labels ||= LabelsFinder.new(current_user, project_id: @project.id).execute.includes(:priorities)
   end
 
   def authorize_admin_labels!