After upgrading Redmine 2.6.1 to Redmine 4,2,2 - Custom Fields shows error

Added by Appandaraj R about 1 month ago

After upgrading Redmine 2.6.1 to Redmine 4.2.2, Internal Error message is displayed on clicking the Custom Fields Link under Administration.

Furnishing below the Error Log :

Started GET "/redmine/custom_fields" for at 2021-09-14 16:05:20 +0530
Processing by CustomFieldsController#index as HTML
Current user: admin (id=1)
Completed 500 Internal Server Error in 80ms (ActiveRecord: 34.8ms)

ActiveRecord::SubclassNotFound (Invalid single-table inheritance type: Issue is not a subclass of CustomField):

app/controllers/custom_fields_controller.rb:32:in `group_by'
app/controllers/custom_fields_controller.rb:32:in `block (2 levels) in index'
app/controllers/custom_fields_controller.rb:30:in `index'
lib/redmine/sudo_mode.rb:61:in `sudo_mode'