Always call kartHit

CTF map can be used without arena, and linear race mode will
override kartHit to do nothing anyway

src/items/flyable.cpp

@@ -565,7 +565,7 @@ void Flyable::explode(AbstractKart *kart_hit, PhysicalObject *object,
             // The explosion animation will register itself with the kart
             // and will free it later.
             ExplosionAnimation::create(kart, getXYZ(), kart==kart_hit);
-            if(kart==kart_hit && Track::getCurrentTrack()->isArena())
+            if (kart == kart_hit)
             {
                 world->kartHit(kart->getWorldKartId(),
                     m_owner->getWorldKartId());