IE 11 Error Canvg.js parser error

Dear,

I am traying to save my chart as image. This works good with Firefox but it
does not work under IE(11). The error is happening with:

if (window.DOMParser)
{
var parser = new DOMParser();
return parser.parseFromString(xml, 'text/xml'); <----- Error
}

has anyone any idea how I can solve this problem?

Thanks