Syntax error when using "default" theme

[mamacdon]

Using this configuration:

window.$docsify = {
        plantuml: {
          skin: "default",
          serverPath: "https://my-plant-uml.server",
          renderAsObject: true,
        }
}

And this input (within a markdown file):

```plantuml
graph forest {
  rankdir=TB;
  nodesep=.20;
  splines="line";
  node [color=Black, shape=box, style="filled", fillcolor=white];

  subgraph cluster {
    label="Cluster"
    graph[color=grey];
    P1 [fillcolor=khaki, style="filled", label="Label"];
    n00 [label="A"]
    n01 [label="B"]
    n02 [label="C", fillcolor=lightblue]

    P1 -- n00;
    n00 -- n01;
    n01 -- n02;
  }
}

The graph fails to render. Opening the object URL, I see this error:

If I switch to the classic theme, the error goes away, and the graph renders as I expected: