Throws an error when used in XHTML context (using Firefox 37), stop working

[herbalite]

When using maphilight with a page served with

application/xhtml+xml;

then Firefox will throw an exception at the line
a.innerHTML = '<v:shape id="vml_flag1" adj="1" />';

I've fixed this by extending the has_VML function using an exception.
Also changed b.adj == "object" to b.adj === "object" to shut up Netbeans from naging about the comparison. But this is not strictly needed to avoid Netscape throwing an error.

has_VML = (function() {
        try {
            var a = document.createElement('div');
            a.innerHTML = '<v:shape id="vml_flag1" adj="1" />';
            var b = a.firstChild;
            b.style.behavior = "url(#default#VML)";
            return b ? typeof b.adj === "object": true;
        }
        catch (err)
        {
            return false;
        }
    })();

Of course, once MSIE 9 is history, the VML part of this plugin could be dropped entirely.