Scan button is not disabled in Play Mode and NullReferenceExceptions are logged when Scanning in the Render Pipeline Converter while in Play Mode

Steps to reproduce:

1. Create a new URP Project
2. Open the RPC (Window > Rendering > Render Pipeline Converter)
3. Enable all Converter checkboxes
4. Enter Play Mode
5. Click the "Scan" button in the RPC Window and observe the Console
6. Close the RPC Window and Exit Play Mode
7. Observe the Console again

Actual results: Scan button is not disabled, an error is logged when scanning, and Converter initialization hangs.

Expected results: Scan button is disabled in Play Mode

Reproducible with versions: 6000.4.0a3, 6000.4.0b4

Not reproducible with versions: 6000.5.0a4

Fixed in: 6000.5.0a1

Could not test with: 6000.0.65f1, 6000.2.15f1, 6000.3.4f1, 6000.4.0a2 (Scan button is not implemented)

Tested on (OS): Windows 11

Notes:
1. The errors start occurring from 6000.4.0b1 and do not reproduce with 6000.4.0a5
2. Error logged when clicking the Scan button:
"NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Search.SearchDatabase.IncrementLoadBytes (UnityEditor.Search.SearchTask`1[T] loadTask, System.Collections.Generic.HashSet`1[T] deletedAssets) (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.Search.SearchDatabase+<>c_DisplayClass107_0.<IncrementalLoad>b_1 () (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.Search.SearchTask`1+<>c_DisplayClass77_0[T].<DispatchWaitForThread>b_0 () (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.Search.Dispatcher+Task.Invoke () (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.Search.Dispatcher.Process (UnityEditor.Search.Dispatcher+Task& task) (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.Search.Dispatcher.Update () (at <4739927896a24b09bce429c4f942903c>:0)
UnityEditor.EditorApplication.Internal_InvokeTickEvents () (at <c44e7a60e9ad492b88da99c20b4d1cdc>:0)"

3. Error logged when exiting Play Mode:
"MissingReferenceException: The object of type 'UnityEditor.Rendering.Converter.RenderPipelineConvertersEditor' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object. Parameter name: target
UnityEngine.Object+MarshalledUnityObject.TryThrowEditorNullExceptionObject (UnityEngine.Object unityObj, System.String parameterName) (at <7e11edc47b2d475c8077267b2d336806>:0)"