Fixed EventTarget.

I guess before we were not getting errors because it woudln't iterate `undefined`. Now we need to check first.

src/core/EventTarget.js

@@ -24,9 +24,13 @@ THREE.EventTarget = function () {
 
 	this.dispatchEvent = function ( event ) {
 
-		for ( var i = 0, l = listeners[ event.type ].length; i < l; i ++ ) {
+		if ( listeners[ event.type ] !== undefined ) {
 
-			listeners[ event.type ][ i ]( event );
+			for ( var i = 0, l = listeners[ event.type ].length; i < l; i ++ ) {
+
+				listeners[ event.type ][ i ]( event );
+
+			}
 
 		}