initialize runes array list for NPC

src/engine/gameManager/NPCManager.java

@@ -460,6 +460,7 @@ public enum NPCManager {
     }
 
     public static void applyRunesForNPC(NPC npc){
+        npc.runes = new ArrayList<>();
         for(int runeID : _runeSetMap.get(npc.runeSetID)){
             RuneBase rb = RuneBase.getRuneBase(runeID);
             CharacterRune toApply = new CharacterRune(rb,npc.getObjectUUID());