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Thank you for reporting a bug to Unity. We have investigated the issue but were unable to reproduce it with the information provided. This can happen due to differences in environment, project setup, or steps taken. We will close this case for now. If you're able to share additional details such as different projects, steps, hardware/software configuration, or logs - please let us know, and we'll be happy to re-evaluate.
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Steps to reproduce:
1. Create new Unity project
2. Open UI Builder window
3. Add element to the Hierarchy (for example Toggle)
4. Delete the added element from Hierarchy
5. Don't save changes in UI Builder
6. Dock UI Builder window to Game tab
Actual results: Error is thrown -
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.UIElements.Bindings.SerializedObjectBindingToBaseField`2[TValue,TField].OnFieldAttached () (at <8b75957d458a4d75a43ae082435fcb46>:0)
UnityEditor.UIElements.Bindings.SerializedObjectBindingBase.OnAttachToPanel (UnityEngine.UIElements.AttachToPanelEvent evt) (at <8b75957d458a4d75a43ae082435fcb46>:0)
UnityEngine.UIElements.EventCallbackFunctor`1[TEventType].Invoke (UnityEngine.UIElements.EventBase evt) (at <f00cec66743041849ac3a6c03ea57396>:0)
UnityEngine.UIElements.EventCallbackRegistry+DynamicCallbackList.Invoke (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at <f00cec66743041849ac3a6c03ea57396>:0)
Expected results: No errors thrown when docking UI Builder window with unsaved changes
Reproducible with versions: 6000.0.54f1, 6000.1.13f1, 6000.2.0b11, 6000.3.0a3
Tested on (OS): Windows 11
Notes:
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