Fix logic in "last used at per application" oauth token list (#32912)

app/models/user.rb

@@ -280,6 +280,15 @@ class User < ApplicationRecord
     save!
   end
 
+  def applications_last_used
+    Doorkeeper::AccessToken
+      .where(resource_owner_id: id)
+      .where.not(last_used_at: nil)
+      .group(:application_id)
+      .maximum(:last_used_at)
+      .to_h
+  end
+
   def token_for_app(app)
     return nil if app.nil? || app.owner != self