Using layout: elk on a diagram that uses clusters breaks the diagram

[yari-dewalt]

Description

When one attempts to use the elk layout on a diagram that uses a cluster node, it results in an error. Changing the layout off of elk renders the diagram as expected.

Steps to reproduce

1. Create a diagram that uses a cluster (subgraph, namespace, etc.)
2. Change the config layout to elk

Screenshots

Code Sample

No response

Setup

• Mermaid version: 11.4.0
• Browser and Version: Firefox Version 131.0.3 (64-bit)

Suggested Solutions

No response

Additional Context

Looks like the issue is with labelHelper() inside addVertex() for the render function.