Correct check for undefined variable

The code was comparing the result of `typeof` with a variable named `undefined`.

As typeof returns a string it should compare to `'undefined'`

src/definitions/modules/popup.js

@@ -415,7 +415,7 @@ $.fn.popup = function(parameters) {
         },
         supports: {
           svg: function() {
-            return (typeof SVGGraphicsElement === undefined);
+            return (typeof SVGGraphicsElement === 'undefined');
           }
         },
         animate: {