Core/Spells: Fixed possible crash for Decimation

Closes #3750

src/server/game/Entities/Unit/Unit.cpp

@@ -8749,7 +8749,7 @@ bool Unit::HandleProcTriggerSpell(Unit* victim, uint32 damage, AuraEffect* trigg
         case 63156:
         case 63158:
             // Can proc only if target has hp below 35%
-            if (!victim->HasAuraState(AURA_STATE_HEALTHLESS_35_PERCENT, procSpell, this))
+            if (!victim || !victim->HasAuraState(AURA_STATE_HEALTHLESS_35_PERCENT, procSpell, this))
                 return false;
             break;
         // Deathbringer Saurfang - Blood Beast's Blood Link