Removing an Enum Property Entry while the Node is in the workspace throws "Removing Invalid MaterialSlot" warning

Steps to reproduce:
1. Create new Unity project using Universal 3D Template
2. Create new Shader Graph Asset in Project window (right-click > Create > Shader Graph > Lit Shader Graph)
3. In Shader Graph window > Blackboard > create Enum property
4. Drag Enum Property to the workspace
5. While Enum property is selected in Blackboard, find Entries section in Graph Inspector > Graph Settings
6. Press “-“ button
7. Observe the Console window

Actual results: A Console warning is thrown when removing an Entry from an Enum property that has been placed in the Shader Graph workspace “Removing Invalid MaterialSlot”

Expected results: No warnings are thrown in the Console when removing an Entry from an Enum property Node placed in the Shader Graph workspace, Entry should be removed cleanly without any errors or warnings

Reproducible with versions: 6000.0.76f1, 6000.3.17f1, 6000.4.10f1, 6000.5.0b11, 6000.6.0a6

Tested on (OS): macOS Tahoe 26.4.1, Ubuntu 24.04

Warning:

Removing Invalid MaterialSlot: 1
UnityEditor.ShaderGraph.Drawing.Inspector.PropertyDrawers.ShaderInputPropertyDrawer:KeywordRemoveEntry (UnityEditorInternal.ReorderableList)
UnityEditorInternal.ReorderableList/Defaults:DrawFooter (UnityEngine.Rect,UnityEditorInternal.ReorderableList) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/ReorderableList.cs:242)
UnityEditorInternal.ReorderableList:DoListFooter (UnityEngine.Rect) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/ReorderableList.cs:1112)
UnityEditorInternal.ReorderableList:DoLayoutList () (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUI/ReorderableList.cs:763)
UnityEditor.GUIView:ProcessEvent (UnityEngine.EntityId,intptr,bool&) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUIView.cs:70)