Fixes skywrath runtime errors, and skywrath will now cast ancient seal at the most dangerous enemy when retreating.
a. When considering ancient seal during retreat, the range calculation was wrong, and had a negative range unless movement speed was 0.
b. When this happened (e.g. when rooted), it returned all nearby enemies instead of one target, causing an error (and preventing any ability use).
Moved GetMostDangerousEnemy to a separate function since it is used in two places.
b. When this happened (e.g. when rooted), it returned all nearby enemies instead of one target, causing an error (and preventing any ability use).