Scripts/Ulduar: Fixes Flame Leviathan entering evade mode if Pursue returns no target

* Pursue is never cast on players at retail, however, being there without a vehicle doesn't prevent the boss from attacking you, nor does it enter evade mode.

Closes #11199
Merge branch '3.3.5' of https://github.com/TrinityCore/TrinityCore into ghbb
更新