Scripts/AzjolNerub: Missing nullptr check in Hadronox. Closes #21258.

src/server/scripts/Northrend/AzjolNerub/AzjolNerub/boss_hadronox.cpp

@@ -366,7 +366,7 @@ public:
         // Safeguard to prevent Hadronox dying to NPCs
         void DamageTaken(Unit* who, uint32& damage) override
         {
-            if (!who->IsControlledByPlayer() && me->HealthBelowPct(70))
+            if ((!who || !who->IsControlledByPlayer()) && me->HealthBelowPct(70))
             {
                 if (me->HealthBelowPctDamaged(5, damage))
                     damage = 0;