Help Simple adding a GameObject to an ObjectField()

For some reason when I try to drag and drop my prefab into the object field it doesn't stick. I'm not sure where I'm going wrong. Maybe it's just a simple mistake. Thanks in advance.

 using System;
 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 [ExecuteInEditMode]
 public class FracObject : MonoBehaviour {
     public GameObject go;
 }

 using System.Collections;
 using System.Collections.Generic;
 using UnityEditor;
 using UnityEngine;
 
 [CustomEditor(typeof(FracObject))]
 public class FracOjectEditor : Editor {
 
     SerializedProperty goprop;
 
     private void OnEnable()
     {
         goprop = serializedObject.FindProperty("go");
     }
 
     public override void OnInspectorGUI()
     {
         goprop.objectReferenceValue = EditorGUILayout.ObjectField(new GUIContent("Source", "Add object to fracture"), goprop.objectReferenceValue, typeof(GameObject), false);
     }
 }