changed the way of nullifying colums

app/models/issue.rb

@@ -86,6 +86,11 @@ class Issue < ActiveRecord::Base
     before_transition any => :closed do |issue|
       issue.closed_at = Time.zone.now
     end
+
+    before_transition closed: :opened do |issue|
+      issue.closed_at = nil
+      issue.closed_by = nil
+    end
   end
 
   class << self

app/services/issues/reopen_service.rb

@@ -10,7 +10,6 @@ module Issues
         execute_hooks(issue, 'reopen')
         invalidate_cache_counts(issue, users: issue.assignees)
         issue.update_project_counter_caches
-        issue.update(closed_by: nil, closed_at: nil)
       end
 
       issue