Removing unused code

Because this method is called by OpenLayers.Function.bindAsEventListener,
which conditionally assigns window.event already, e cannot be null or
undefined here.

lib/OpenLayers/Handler/MouseWheel.js

@@ -163,9 +163,6 @@ OpenLayers.Handler.MouseWheel = OpenLayers.Class(OpenLayers.Handler, {
         if (!overScrollableDiv && overMapDiv) {
             if (allowScroll) {
                 var delta = 0;
-                if (!e) {
-                    e = window.event;
-                }
                 
                 if (e.wheelDelta) {
                     delta = e.wheelDelta;