Fix weird Rails bug that leads to `runner_id=null` in SQL query

app/services/ci/register_job_service.rb

@@ -89,7 +89,9 @@ module Ci
     end
 
     def builds_for_group_runner
-      hierarchy_groups = Gitlab::GroupHierarchy.new(runner.groups).base_and_descendants
+      # Workaround for weird Rails bug, that makes `runner.groups.to_sql` to return `runner_id = NULL`
+      groups = Group.joins(:runner_namespaces).merge(runner.runner_namespaces)
+      hierarchy_groups = Gitlab::GroupHierarchy.new(groups).base_and_descendants
       projects = Project.where(namespace_id: hierarchy_groups)
         .with_group_runners_enabled
         .with_builds_enabled