Core/Server: Use nullptr instead of 0 where pointers are expected

src/server/game/AI/SmartScripts/SmartAI.cpp

@@ -931,7 +931,7 @@ class SmartTrigger : public AreaTriggerScript
 
         SmartTrigger() : AreaTriggerScript("SmartTrigger") { }
 
-        bool OnTrigger(Player* player, AreaTriggerEntry const* trigger)
+        bool OnTrigger(Player* player, AreaTriggerEntry const* trigger) override
         {
             if (!player->IsAlive())
                 return false;