ShowObjectPicker freezes Unity

Hello,
I've had a problem with ShowObjectPicker().
The goal would be: as the user opens the TriggerChoiceWindow, the ObjectPicker window shows up, and the user can choose the object out of a selection. The chosen object would then be in an ObjectField.
The problem is, using the ShowObjectPicker function freezes Unity.
Here is the code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEditor;
5.  
6. public class TriggerChoiceWindow : EditorWindow {
7.  
8.     [MenuItem("Window/TriggerChoice")]
9.     public static void ShowWindow()
10.     {
11.         EditorWindow.GetWindow(typeof(TriggerChoiceWindow));
12.     }
13.  
14.     int currentPickerWindow;
15.     public Object selectedObject;
16.  
17.     void ShowPicker()
18.     {
19.         currentPickerWindow = EditorGUIUtility.GetControlID(FocusType.Passive);
20.         EditorGUIUtility.ShowObjectPicker<Object>(null, false, "Cube", currentPickerWindow);
21.     }
22.  
23.     void OnGUI()
24.     {
25.         ShowPicker();
26.         if (Event.current.commandName == "ObjectSelectorUpdated" && EditorGUIUtility.GetObjectPickerControlID() == currentPickerWindow)
27.         {
28.             selectedObject = EditorGUIUtility.GetObjectPickerObject();
29.             EditorGUILayout.ObjectField(selectedObject, typeof(Object), true);
30.             currentPickerWindow = -1;
31.             Debug.Log(selectedObject.name);
32.         }
33.     }
34. }
35.  

Unity doesn't freeze instantly; it does try to display the selected object's name, but it throws a NullReferenceException. After several tries, I've found that it's the line with ShowObjectPicker that causes Unity to freeze. Without that line, Unity just works normally.

I hope someone can help me. Thank you for your time.