JS error in imagediff.js

[wxiaoguang]

caught by #18971 (Show JS errors) , reported by a user.

caused by imagediff.js

function getDefaultSvgBoundsIfUndefined(svgXml, src) {
  const DefaultSize = 300;
  const MaxSize = 99999;

  const svg = svgXml.rootElement; // BUG, here svg might be null, then the following `svg.width` triggers JS error

  const width = svg.width.baseVal;
  const height = svg.height.baseVal;
  if (width.unitType === SVGLength.SVG_LENGTHTYPE_PERCENTAGE || height.unitType === SVGLength.SVG_LENGTHTYPE_PERCENTAGE) {

Compiled JS, the index.js:37:1821 is at c=o.width

o=e.rootElement,c=o.width.baseVal,y=o.height.baseVal;if(c.unitType===SVGLength.SVG_LENGTHTYPE_PERCENTAG

[KN4CK3R]

Do you have an example svg?

[wxiaoguang]

No, I have asked but the reporter can not provide more information.

[wxiaoguang]

I managed to reproduce it. See https://try.gitea.io/wxiaoguang/test/pulls/6/files

[wxiaoguang]

I proposed a fix #19494