Currently if a unit is missing an animation, the game will fallback to the idle anim, which is good in theory, but doesn't allow for someone to have mixed anims in a group, or if we were to extend the garrison holder to play a specific variant, or it's closest fallback.
TODO: This is not efficient. I believe the entire function could be smarter. While at it, one could look at the map storing all anim names to optimize that as well see the relevant todo in objectentry.h l93
// TODO: something more memory-efficient than storing loads of similar strings for each unit?