Problems with rendering of Flowchart

[timonkrebs]

Describe the bug
I am building a FlowChart generation tool for Angular applications.
It works quite good but for one app I get no error but also no chart is generated.

To Reproduce
Link to Live Editor:
Link to Live Editor

I encountered a console error:

Expected behavior
I would expect a FlowChart to be rendered or an error to be shown that helps me figure out what the Problem might be with the mermaid definition.

Screenshots
When I try to export the graph it says: Cannot set properties of undefined (setting 'rank')

Desktop (please complete the following information):

• OS: Windows
• Browser Chrome, Firefox, Edge