Leaking Materials When Drawing Text Gizmo

I am using Shapes to draw a text gizmo into my scene to make designing levels easier. I only want this Gizmo in the editor. I created a CustomLabel component which draws some text but it emits an error when doing so.

The error:

Instantiating material due to calling renderer.material during edit mode. This will leak materials into the scene. You most likely want to 
use renderer.sharedMaterial instead 

UnityEngine.Renderer:get_material ()
TMPro.TextMeshPro:SetOutlineColor (UnityEngine.Color32) (at ./Library/PackageCache/com.unity.textmeshpro@3.0.6/Scripts/Runtime/TMPro_Private.cs:867)
TMPro.TMP_Text:set_outlineColor (UnityEngine.Color32) (at ./Library/PackageCache/com.unity.textmeshpro@3.0.6/Scripts/Runtime/TMP_Text.cs:424)
Project.CustomLabel:OnDrawGizmos () (at Assets/_Project/_Code/_Scripts/Action/CustomLabel.cs:31)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)

The script:

using System;
using Shapes;
using TMPro;
using UnityEngine;

namespace Project
{
    public class CustomLabel : MonoBehaviour
    {
        [SerializeField]
        private string _text = "";

        [NonSerialized]
        private TextElement? _textElement;

        private void OnDrawGizmos()
        {
            if (_textElement == null)
            {
                _textElement = new TextElement();
                TextMeshPro? tmp = _textElement.Tmp;

                if (tmp == null)
                {
                    return;
                }
                
                tmp.color = Color.white;
                tmp.outlineColor = Color.black;
                tmp.outlineWidth = 5;
            }

            Vector3 position = transform.position;

            Draw.Text(_textElement, position, _text);
        }
    }
}