added check if dragImage exists (for IE)
added check if dragImage exists (for IE)

voidberg/html5sortable,lukasoppermann/html5sortable,nazar-pc/html5sortable,xiwc/html5sortable,illsism/html5sortable,nazar-pc/html5sortable,voidberg/html5sortable,lukasoppermann/html5sortable,lukasoppermann/html5sortable,xiwc/html5sortable,illsism/html5sortable