Three.js - Remove the head of an ArrowHelper

I have created in my code an ArrowHelper and I update its parameters by calling the function below (each call of this function updates the ArrowHelper dimensions) :

function updateArrowHelper() {



    // Update parameters for transportedVector

    transportedVector.arrowHelper.setLength(transportedVector.coordLocal.length(), headLengthVector, headWidthVector);

  transportedVector.arrowHelper.setDirection(directionVector.normalize());

  transportedVector.arrowHelper.position.copy(coordTorus);

  transportedVector.arrowHelper.line.material.linewidth = widthVector;

  transportedVector.arrowHelper.setColor(hexVector);

  // Set head length and width to zero if dirVector.length is zero

  if (transportedVector.coordLocal.length() == 0.0)

        transportedVector.arrowHelper.setLength(0, 0, 0);    

}

I would like to make disappear the head of if its length (given by ) is zero, what I have done with :

 // Set head length and width to zero if dirVector.length is zero

      if (transportedVector.coordLocal.length() == 0.0)

        transportedVector.arrowHelper.setLength(0, 0, 0);

But at the execution, this doesn't work : even the length is null, once function is called, the head is still displayed and I don't know why ?

If anyone could see what's wrong.

Thanks in advance.