Scripts/Naxxramas: Fix Kel'thuzad evade mode when he dies (#24763)

src/server/scripts/Northrend/Naxxramas/boss_kelthuzad.cpp

@@ -232,8 +232,12 @@ public:
                 _abominationDeathCount = 0;
                 _phaseThree = false;
             }
+
             void EnterEvadeMode(EvadeReason /*why*/) override
             {
+                if (!me->IsAlive())
+                    return;
+
                 for (NAXData64 portalData : portalList)
                     if (GameObject* portal = ObjectAccessor::GetGameObject(*me, instance->GetGuidData(portalData)))
                         portal->SetGoState(GO_STATE_READY);