Redmine Matrix Field

GitHub tests are failing due to an ActiveModel::UnknownAttributeError: unknown error. It complains

 RedmineMatrixField::FormulaValidatorTest#test_should_complain_wrong_delimiter [/home/runner/work/redmine_matrix_field/redmine_matrix_field/redmine/plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:44]:
[ActiveRecord::RecordInvalid] exception expected, not
Class: <ActiveModel::UnknownAttributeError>
Message: <"unknown attribute 'formula' for IssueCustomField.\n\n          raise UnknownAttributeError.new(self, k.to_s)\n          ^^^^^">
---Backtrace---
plugins/redmine_matrix_field/test/methods_helper.rb:88:in `computed_field'
plugins/redmine_matrix_field/test/methods_helper.rb:107:in `computed_field_combi_matrix'
plugins/redmine_matrix_field/test/methods_helper.rb:73:in `field_with_combi_matrix_format'
plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:54:in `public_send'
plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:54:in `field_validation'
plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:45:in `block (2 levels) in <class:FormulaValidatorTest>'
plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:44:in `block in <class:FormulaValidatorTest>'
---------------

rails test plugins/redmine_matrix_field/test/unit/formula_validator_test.rb:43

See https://github.com/xmera-circle/redmine_matrix_field/actions/workflows/5-0-stable.yml for details.