Merge branch 'sh-fix-api-exception-handling' into 'master'

Ensure #route_setting is available before calling it

See merge request !2908

changelogs/unreleased-ee/sh-fix-api-exception-handling.yml

+---
+title: 'Ensure #route_setting is available before calling it'
+merge_request: 2908
+author:
+type: fixed

lib/api/api_guard.rb

@@ -106,6 +106,8 @@ module API
       private
 
       def route_authentication_setting
+        return {} unless respond_to?(:route_setting)
+
         route_setting(:authentication) || {}
       end