Steps to reproduce:

1. Open a Unity project
2. Window → Search → New Window
3. Immediately dock the Search window
4. Ensure Toggle Search Query Builder Mode is ON
5. Click Toggle Saved Search Panel
6. In Builtins/Reports, select any option
7. Undock the Search window

\\
Actual results: 
{code:java}
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Search.SearchQueryBuilderView.OnAttachToPanel (UnityEngine.UIElements.AttachToPanelEvent evt) (at /Users/bokken/build/output/unity/unity/Modules/QuickSearch/Editor/UITK/SearchQueryBuilderView.cs:73)
UnityEngine.UIElements.EventCallbackFunctor`1[TEventType].Invoke (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventCallback.cs:64)

{code}

Expected results: Undocking should not throw; SearchQueryBuilderView should reattach cleanly

\\
Reproducible with versions: 6000.3.0b1

Can’t test with versions: 6000.0.56f1, 6000.1.16f1, 6000.2.4f1, 6000.3.0a1 (No Builtin dropdown sections)

\\
Tested on (OS): Ubuntu 22.04, macOS 15.6