AnimationObjectGroup clean up.

src/animation/AnimationObjectGroup.js

@@ -96,7 +96,7 @@ Object.assign( AnimationObjectGroup.prototype, {
 			parsedPaths = this._parsedPaths,
 			bindings = this._bindings,
 			nBindings = bindings.length,
-		    	knownObject = undefined;;
+		    	knownObject = undefined;
 
 		for ( var i = 0, n = arguments.length; i !== n; ++ i ) {