Steps to reproduce:
1. Create new Unity project
2. In Hierarchy window create “NavMesh Link” GO (Right-click > AI > NavMesh Link)
3. Select “NavMesh Link” GO in Hierarchy window
4. In Inspector window click on Agent Type > Humanoid
5. From dropdown menu select “Open Agent Settings…”
6. Observe Console window

Actual results: Error is thrown in the Console window: “InvalidOperationException: Stack empty.
System.Collections.Generic.Stack`1[T].Pop () (at :0)
UnityEditor.EditorGUI.EndProperty () (at /home/bokken/build/output/unity/unity/Editor/Mono/EditorGUI.cs:7082)
Unity.AI.Navigation.Editor.NavMeshComponentsGUIUtility.AgentTypePopup (UnityEngine.GUIContent label, UnityEditor.SerializedProperty agentTypeID) (at ./Library/PackageCache/com.unity.ai.navigation@5218e4bf7edc/Editor/NavMeshComponentsGUIUtility.cs:120)
Unity.AI.Navigation.Editor.NavMeshLinkEditor.OnInspectorGUI () (at ./Library/PackageCache/com.unity.ai.navigation@5218e4bf7edc/Editor/NavMeshLinkEditor.cs:118)
UnityEditor.UIElements.InspectorElement+<>c_{_}DisplayClass82_0.<CreateInspectorElementUsingIMGUI>b{_}_2 () (at /home/bokken/build/output/unity/unity/Editor/Mono/UIElements/Inspector/InspectorElement.cs:795)
UnityEditor.PopupCallbackInfo:SetEnumValueDelegate(Object, String[], Int32) (at /home/bokken/build/output/unity/unity/Editor/Mono/EditorGUI.cs:4093)”

Expected results: No errors thrown in the Console window

Reproducible with versions: 2.0.7 (6000.3.0a2 (d454866889d5)), 2.0.9 (6000.3.3f1, 6000.4.0b3, 6000.5.0a4) 

Not reproducible with versions: 6000.0.65f1, 6000.2.15f1, 2.0.7 (6000.3.0a1 (4592b02ab560))

Tested on (OS): Ubuntu 24.04

Notes:

• Was not able to reproduce the issue on macOS Silicon Tahoe 26.2