问为什么对于无法到达的目的地，NavMeshAgent.remainingDistance会返回无穷大的值，然后在Unity中返回一个浮点数？

EN

public static class ExtensionMethods
{
    public static float GetPathRemainingDistance(this NavMeshAgent navMeshAgent)
    {
        if (navMeshAgent.pathPending ||
            navMeshAgent.pathStatus == NavMeshPathStatus.PathInvalid ||
            navMeshAgent.path.corners.Length == 0)
            return -1f;

        float distance = 0.0f;
        for (int i = 0; i < navMeshAgent.path.corners.Length - 1; ++i)
        {
            distance += Vector3.Distance(navMeshAgent.path.corners[i], navMeshAgent.path.corners[i + 1]);
        }

        return distance;
    }
}

public float GetRemainingDistance()
{
     float distance = 0;
     Vector3[] corners = m_navMeshAgent.path.corners;

     if (corners.Length > 2)
     {
           for (int i = 1; i < corners.Length; i++)
           {
                 Vector2 previous = new Vector2(corners[i - 1].x, corners[i - 1].z);
                 Vector2 current = new Vector2(corners[i].x, corners[i].z);

                 distance += Vector2.Distance(previous, current);
           }
     }
     else 
     {
           distance = m_navMeshAgent.remainingDistance;
     }
   
     return distance;
}