fix(Scripts/Vehicles): The next player entering Salvaged Siege Engine… (#10987)

… should control turret if it's not occupied.

src/server/game/AI/CreatureAI.h

@@ -177,6 +177,8 @@ public:
     /// == Fields =======================================
     virtual void PassengerBoarded(Unit* /*passenger*/, int8 /*seatId*/, bool /*apply*/) {}
 
+    virtual bool BeforeSpellClick(Unit* /*clicker*/) { return true; }
+
     virtual void OnSpellClick(Unit* /*clicker*/, bool& /*result*/) { }
 
     virtual bool CanSeeAlways(WorldObject const* /*obj*/) { return false; }