It appears this is working correctly and gives the same result if you use:
element.style.height
Since no inline style or CSS height is set on the element a blank line is shown. Instead of relying on the style you can get the HTML elements height directly.
console.log(element[0].offsetHeight);
http://plnkr.co/edit/03YWwjBjYpid4fVmDxlM?p=preview
How do I retrieve an HTML element’s actual width and height?