Possible bug in Spritesheet update

I have found a possible bug in the AnimatedSprite.hx class of Spritesheet lib:
if I try to update a symbol that has no behaviour set it fails at line 133:

if (currentBehavior.loop) {

because currentBehavior is null.
I think it is necessary to put a precondition to execute the whole update function

public function update (deltaTime:Int):Void {
	if (currentBehavior != null) {

yep, that makes sense. Pull request?