CustomLabelDrawer.cs

using UnityEngine;
using UnityEditor;

[CustomPropertyDrawer(typeof(LabelAttribute), true)]
public class CustomLabelDrawer : PropertyDrawer
{
    public override void OnGUI(Rect rect, SerializedProperty property, GUIContent label)
    {
        try
        {
            EditorGUI.PropertyField(rect, property, new GUIContent(((LabelAttribute)attribute).Label));
        }
        catch
        {
            EditorGUI.PropertyField(rect, property, label);
        }
    }
}