Wither spawn had some issue after 1.12

It seems that the wither spawn animation had been broken after 1.12 bedrock.

Wither can fly when they spawn and the spawn animation not been shown correctly.

The reason of the animation broken is query.overlay_alpha is deprecated and will be removed.

Mojang need change the wither_boss.render_controllers.json files.

      "overlay_color":

{         "r": "variable.is_invulnerable ? 1.0 : this",         "g": "variable.is_invulnerable ? 1.0 : this",         "b": "variable.is_invulnerable ? 1.0 : this",         "a": "variable.is_invulnerable ? query.overlay_alpha : this"       }

A possible solution is change the alpha like this:
 "a": "variable.is_invulnerable ? Math.max(1.0 - query.anim_time * 0.2, 0) : this"