Fixed exception when played earlier than Awake/Start

[azukizuki]

Hi, thanks for implement great library!

I found a one issue.
about Play() method in AnimatedImage is throw NullReferenceException when called before awake and start method.

this problem is occured like this code.

_animatedImage.Play();
this.gameObject.SetActive(true);

I try to fixed it.
I implement of Delay the call to the Play method until becomes active of gameObject.
could you check is it?