Memory leak when trying to render a subworkflow

[multimeric]

If you use cwl-svg to render a CWL workflow, and then use workflow.draw() on another workflow that was originally inside the original workflow, the page will get stuck in an infinite loop and in my case, crash your browser.

To demonstrate, the simplest case I can recreate is here: https://github.com/TMiguelT/CwlSvgBug (instructions included)