Error when using <polygon />

[Undistraction]

Firstly, thank you. This library is really wonderful. I have spent most of the day playing with it.

When SVG markup contains a polygon, for example:

<polygon points="53.4,44 389.3,204.8 74.7,312.6 "/>

The following error occurs:

Uncaught TypeError: e.append is not a function
    at Object.i [as polygon] (shape.js:24)
    at Object.polygon (normalize.js:33)
    at i (normalize.js:76)
    at new e (Warp.js:16)
    at pen.js:6
i @ shape.js:24
polygon @ normalize.js:33
i @ normalize.js:76
e @ Warp.js:16
(anonymous) @ pen.js:6

Please see my fork of your Codepen here which clearly shows the error. Verified in Chrome and Firefox (Mac).