Oh Noes renders HTML tags when ProcessingJS throws an error

Try a program with just:

bezierVertex(100, 10, 20, 20, 20, 20);

You'll then see:

Oh noes!
vertex() must be used at least once before calling bezierVertex()

ProcessingJS throws() the text, and then we wrap it in the span but display it as text:

if (typeof error === "string") {
newError.text = this.clean(this.prettify(error));
}

I wonder if we actually need to call prettify() in that situation- perhaps not. I'm not sure what other situations trigger that code path.

Reproduce the issue with the bezierVertex() example, then trace the string-error branch containing clean() and prettify(). Check how the resulting error text is rendered and verify that the displayed message shows the intended text without literal HTML tags.

Written by the indexing model from the issue text.