"NullReferenceException" is thrown in the Console when creating an “Animation Play State Style Enum Field" from UI Library

Unity: UI Toolkit Authoring Framework

Fixed

6.6.X

6000.6.0b1

Steps to reproduce:
1. Create new Unity project using Universal 3D Template
2. Open UI Library window (right-click in Hierarchy > UI Toolkit > Standard Elements > UI Library)
3. In UI Library find “Animation Play State Style Enum Field ” and double click on it to create it
4. In “Open UI stage” pop-up press “Continue” and save UXML file
5. Once the files are created, observe the Console window

Actual results: “NullReferenceException: Object reference not set to an instance of an object” errors are thrown in the Console window

Expected results: No errors are thrown in the Console window

Reproducible with versions: 6000.6.0a7

Can’t test with versions: 6000.6.0a6 and lower (No such feature to create UI Elements in Hierarchy window)

Tested on (OS): macOS Tahoe 26.4.1 (M1)

NullReferenceException: Object reference not set to an instance of an object
Unity.UIToolkit.Editor.LiveAttributePropertyController.CollectLiveAttributeValuePropertyModifications (System.Object obj, System.Object uxmlSerializedData, UnityEditor.UIElements.UxmlSerializedAttributeDescription attributeDescription, UnityEditor.SerializedProperty property, System.Collections.Generic.List`1[T] propertyModifications, System.Boolean& hasUnsupportedDrivenPropertyChange, System.Boolean syncOnlyBoundValues, System.Collections.Generic.HashSet`1[T] resolvedBindingLookup) (at /Users/bokken/build/output/unity/unity/Modules/UIToolkitAuthoringEditor/Managed/Inspector/Controls/LiveAttributePropertyController.cs:173)
Rethrow as Exception: Failed to collect modifications validation
UnityEngine.Debug:LogException(Exception)
Unity.UIToolkit.Editor.LiveAttributePropertyController:CollectLiveAttributeValuePropertyModifications(Object, Object, UxmlSerializedAttributeDescription, SerializedProperty, List`1, Boolean&, Boolean, HashSet`1) (at /Users/bokken/build/output/unity/unity/Modules/UIToolkitAuthoringEditor/Managed/Inspector/Controls/LiveAttributePropertyController.cs:338)

"NullReferenceException" is thrown in the Console when creating an “Animation Play State Style Enum Field" from UI Library

Unity: UI Toolkit Authoring Framework

Fixed

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"NullReferenceException" is thrown in the Console when creating an “Animation Play State Style Enum Field" from UI Library

Unity: UI Toolkit Authoring Framework

Statuses

Fixed

Resolution Notes

Description

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Have a workaround or additional info about this issue?