Find if no objects with tag exist

I have several waypoints with a tag "waypoint1" with govern the movement. However, I would like to check if any of them exist before attempting to move.

The problem I have is that it completely ignored the 'if null' check. How can I get that to work?

waypointNumber is a string.

This is my current code which doesn't work

void OnTriggerStay(Collider other)
{
    if (other.tag == waypointNumber)
    {
        Debug.Log("hit");
        if (other.transform.position == nextWaypoint)
        {
            Destroy(other.gameObject);

            if (GameObject.FindGameObjectsWithTag(waypointNumber) == null)
            {
                Debug.Log("null!");
                allowMove = false;
            }

            GameObject[] waypointArray = GameObject.FindGameObjectsWithTag(waypointNumber);
            nextWaypoint = waypointArray[1].transform.position;
        }
    }
}

I have tried using:

if (GameObject.FindGameObjectsWithTag(waypointNumber) != null{}else{DoStuff}

With no results.

I tried the waypointArray.Length == 0 like this:

if (other.transform.position == nextWaypoint)
        {
            Destroy(other.gameObject);

            GameObject[] waypointArray = GameObject.FindGameObjectsWithTag(waypointNumber);

            if (waypointArray.Length == 0)
            {
                Debug.Log("null!");
                allowMove = false;
            }

            nextWaypoint = waypointArray[1].transform.position;
        }

It ignored the "if (waypointArray.Length == 0)" and jumped straight to nextWaypoint = ... The console gave the error of "IndexOutOfRangeException: Array index is out of range."

Odd. I wonder if it returns an array of zero length? Could you try that? (Docs say null though)

Try this: if (!GameObject.FindGameObjectsWithTag(waypointNumber))

The sign of negation (!) should be placed early in the condition as the example

So try to store GameObject.FindGameObjectsWithTag (waypointNumber) and put a variable like this:

var waypointsNumber // is an array if (! waypointsNumber) { // Place your code here }