Can't submit workflows with Argo Workflows UI

The Argo workflows UI ([https://argo-workflows.workflows.diamond.ac.uk](https://argo-workflows.workflows.diamond.ac.uk)) currently does not allow to submit a workflow from the Cluster Workflow Templates tab. The namespace seems to be set as "undefined".

Resubmitting existing workflows works fine (because namespace is already stored in the workflow) and submitting workflows with `kubectl` also works fine.