If a style value that ends in ; is used (i.e. color: #FF0000;) then the parser send's setStyle('colour', '#FF0000') and setStyle('', '').

The second call with a key that is empty, triggers an error in IE8 (and possibly below) when the code hits the @node.style[key] = value code below.
As I assume we should ignore blank keys, I just return false immediately.

Very difficult to test, as it works fine on all modern browsers.