If an animation is really just a plain image (has only one frame),
this function returns that image.
If the animation is an animation, this function returns a reasonable
image to use as a static unanimated image, which might be the first
frame, or something more sophisticated depending on the file format.
If an animation hasn't loaded any frames yet, this function will
return NULL.
Retrieves a static image for the animation.
If an animation is really just a plain image (has only one frame), this function returns that image.
If the animation is an animation, this function returns a reasonable image to use as a static unanimated image, which might be the first frame, or something more sophisticated depending on the file format.
If an animation hasn't loaded any frames yet, this function will return NULL.