Fixes #4454 - Exchange Oauth token update job is always marked as failed job when it's not configured.

lib/external_credential/exchange.rb

@@ -124,7 +124,7 @@ class ExternalCredential::Exchange
 
   def self.refresh_token
     config = Setting.get('exchange_oauth')
-    return if config.blank?
+    return {} if config.blank?
     return config if config[:created_at] >= 50.minutes.ago
 
     params = refresh_token_params(config)

spec/lib/external_credential/exchange_spec.rb

@@ -0,0 +1,11 @@
+# Copyright (C) 2012-2023 Zammad Foundation, https://zammad-foundation.org/
+
+require 'rails_helper'
+
+RSpec.describe ExternalCredential::Exchange do
+  describe "Exchange Oauth token update job is always marked as failed job when it's not configured #4454", performs_jobs: true do
+    it 'does always return a value' do
+      expect(described_class.refresh_token).to be_truthy
+    end
+  end
+end