修复一个aoi报错的bug

Unity/Assets/Scripts/Hotfix/Server/Module/AOI/AOIManagerComponentSystem.cs

@@ -52,13 +52,12 @@ namespace ET.Server
                 return;
             }
 
-            Fiber fiber = self.Fiber();
             // 通知订阅该Cell Leave的Unit
             aoiEntity.Cell.Remove(aoiEntity);
             foreach (KeyValuePair<long, EntityRef<AOIEntity>> kv in aoiEntity.Cell.SubsLeaveEntities)
             {
                 AOIEntity e = kv.Value;
-                e.LeaveSight(aoiEntity);
+                e?.LeaveSight(aoiEntity);
             }
 
             // 通知自己订阅的Enter Cell，清理自己