TypeError: Cannot set properties of undefined (setting 'rank') when pointing a node to a subgraph

[hyperrecursive]

Here is the example code:

```mermaid
graph LR
    subgraph sg0
        node0 --> sg1
        node0 --> node2
        subgraph sg1
            node3
        end
        subgraph sg2
        end
    end
```

In VS Code (and GitHub as well), the following error is printed:

TypeError: Cannot set properties of undefined (setting 'rank')

It should be possible according to #644. This is how it is rendered in the live editor:

[mjbvz]

Renders fine for me in the latest extension version:

[hyperrecursive]

I've just tested it again and found out that the Markdown Preview Enchanced steals the rendering of Mermaid diagrams if both extensions are enabled.