When using `OnAudioFilterRead` with an `AudioListener`, a null reference error is thrown in the console.

Repro

1. Download and open the attached project `OAFR Error Repro.zip`.
2. Open SampleScene.
3. Click on the Main Camera game object.

Expected: No error is thrown in the console and the `OAFR` component shows the VU meter.

Actual: A null reference error is thrown in the console, but the `OAFR` component does show the VU meter.

Regression details

This is related to the VU meter implementation, which was absent through versions 2022.2.0a9 (see bisection comment) to 2023.3.0a13 (PR). The same problem is present in 2022.2.0a8 when the VU meter was still there, so that PR should not be marked as the one that regressed.

Reproducible on 2022.3.X, 2023.2.X, and 2023.3.X

Not reproducible on 2021.3.34f1.

Stack trace
{code:java}
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.AudioFilterGUI.DrawAudioFilterGUI (UnityEngine.MonoBehaviour behaviour) (at /Users/kristinnbragi/gitrepo/trunk/Editor/Mono/Inspector/AudioFilterGUI.cs:42)
UnityEditor.Audio.UIElements.OnAudioFilterReadLevelMeter+<>c__DisplayClass1_0.<.ctor>b__0 () (at /Users/kristinnbragi/gitrepo/trunk/Editor/Mono/Audio/UIElements/OnAudioFilterReadLevelMeter.cs:12)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/IMGUIContainer.cs:396)
UnityEngine.DebugLogHandler:Internal_LogException_Injected(Exception, IntPtr)
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
UnityEngine.UIElements.IMGUIContainer:DoOnGUI(Event, Matrix4x4, Rect, Boolean, Rect, Action, Boolean) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/IMGUIContainer.cs:411)
UnityEngine.UIElements.IMGUIContainer:DoMeasure(Single, MeasureMode, Single, MeasureMode) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/IMGUIContainer.cs:882)
UnityEngine.UIElements.VisualElement:Measure(VisualElement, LayoutNode&, Single, LayoutMeasureMode, Single, LayoutMeasureMode, LayoutSize&) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/VisualElement.cs:2190)
UnityEngine.UIElements.Layout.LayoutDelegates:InvokeMeasureFunction(LayoutNode&, Single, LayoutMeasureMode, Single, LayoutMeasureMode, LayoutSize&) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Layout/LayoutProcessor.cs:75)
UnityEngine.UIElements.Layout.LayoutNative:CalculateLayout(IntPtr, Single, Single, Int32, IntPtr)
UnityEngine.UIElements.Layout.LayoutProcessorNative:UnityEngine.UIElements.Layout.ILayoutProcessor.CalculateLayout(LayoutNode, Single, Single, LayoutDirection) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Layout/Native/LayoutProcessorNative.cs:35)
UnityEngine.UIElements.Layout.LayoutProcessor:CalculateLayout(LayoutNode, Single, Single, LayoutDirection) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Layout/LayoutProcessor.cs:32)
UnityEngine.UIElements.Layout.LayoutNode:CalculateLayout(Single, Single) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Layout/LayoutNode.cs:324)
UnityEngine.UIElements.UIRLayoutUpdater:Update() (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Renderer/UIRLayoutUpdater.cs:152)
UnityEngine.UIElements.VisualTreeUpdater:UpdateVisualTreePhase(VisualTreeUpdatePhase) (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/VisualTreeUpdater.cs:116)
UnityEngine.UIElements.Panel:UpdateWithoutRepaint() (at /Users/kristinnbragi/gitrepo/trunk/Modules/UIElements/Core/Panel.cs:1266)
UnityEditor.EditorElementUpdater:CreateInspectorElementsForViewport(ScrollView, VisualElement) (at /Users/kristinnbragi/gitrepo/trunk/Editor/Mono/Inspector/EditorElementUpdater.cs:104)
UnityEditor.PropertyEditor:RebuildContentsContainers() (at /Users/kristinnbragi/gitrepo/trunk/Editor/Mono/Inspector/Core/PropertyEditor.cs:1186)
UnityEditor.InspectorWindow:RedrawFromNative() (at /Users/kristinnbragi/gitrepo/trunk/Editor/Mono/Inspector/Core/InspectorWindow.cs:202) {code}