动画为空
错误提示：
The animation state run could not be played because it couldn't be found!
Please attach an animation clip with the name 'run' or call this function only for existing animations.
UnityEngine.Animation:Play(String)
wukongMove:Update() (at Assets/wukongMove.cs:17)
解决方案：
动画不为空，或者后台不调用此动画
