Only attempt to use the IE technique for setting opacity if the filte…

…r property exists (otherwise fallback to the standards-compatible technique).

src/css.js

@@ -49,7 +49,7 @@ jQuery.extend({
 		var style = elem.style || elem, set = value !== undefined;
 
 		// IE uses filters for opacity
-		if ( !jQuery.support.opacity && name === "opacity" ) {
+		if ( !jQuery.support.opacity && name === "opacity" && style.filter ) {
 			if ( set ) {
 				// IE has trouble with opacity if it does not have layout
 				// Force it by setting the zoom level