sticky: null-pointer exception

[Frank3K]

Commit 08bf4f9 introduced a null-pointer exception in sticky.js. The null-pointer is on line 194:

      while (current && current !== contentEl[0]) {
        item.top += current.offsetTop;
        item.left += current.offsetLeft;
        item.right += current.offsetParent.offsetWidth - current.offsetWidth - current.offsetLeft; //Compute offsetRight
        current = current.offsetParent;
      }

In the above loop, current.offsetParent can be null.