unity报错："SetDestination" can only be called on an active agent that has been placed on a NavMesh. UnityEngine.AI.NavMeshAgent:set_destination(Vector3) Enemy.<enemyPatrol>d__5:MoveNext() (at Assets/DiffuseRoad/EnemyScripts/EnemyPatrolController.cs:34) UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)
产生错误的原因是，代理(NavMeshAgent)不在网格（NavMesh）上，
排除错误的方法：
一、查看NavMeshAgent是否在网格上。
二、烘培所用的AgentType和NavMeshAgent的AgentType是否为同一种类型。
三、没有烘培NavMesh或者场景调整后，NavMesh没有及时的重新烘焙（Bake)
