AltImage via set/highlight/select triggers exception

[techfg]

When trying to establish an exception similar to the following occurs:

graphics.js:215 Uncaught TypeError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The provided value is not of type '(CSSImageValue or HTMLImageElement or SVGImageElement or HTMLVideoElement or HTMLCanvasElement or ImageBitmap or OffscreenCanvas)'
    at m.Graphics.addAltImage (graphics.js:215)
    at m.Graphics.<anonymous> (graphics.js:438)
    at Object.<anonymous> (graphics.js:253)
    at Function.each (jquery.1.7.2.min.js:2)
    at m.Graphics.render (graphics.js:249)
    at m.Graphics.addShapeGroup (graphics.js:156)
    at m.AreaData.highlight (areadata.js:248)
    at HTMLAreaElement.mouseover (mapdata.js:162)
    at HTMLAreaElement.me.mouseover (mapdata.js:359)
    at HTMLAreaElement.dispatch (jquery.1.7.2.min.js:3)

It appears this issue was introduced in this commit with the root cause being Line 1034.

Steps to reproduce:

1. Clone repo
2. Open /examples/altimages.js
3. Hover over Texas
   OR
4. Click "click to bind az with altimage2"