NullReferenceException occurs on selecting SignalEmitter preset asset.

Steps to repro:
1. Open the attached project.
2. Windows > Sequencing > Timeline.
3. Select Cube in the Hierarchy.
4. Click on Vertical Ellipsis(Three Vertical Dots) on playable track.
5. Add Signal Emitter > Create Preset of Signal Emitter and Save.
6. Select newly created Preset Asset in the Project Window.

Actual Result:
NullReferenceException occurs.

Expected Result:
The Exception should not occur in the console.

Reproducible in:
2019.3.0a4, 2019.2.0b4, 2019.1.0b9.

Working Fine in:
2019.1.0b8.

Environment:
Windows & Mac.

NOTE: Signal Emitter is introduced in 2019.1.

Stacktrace:

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Timeline.Signals.SignalEmitterInspector.GetBoundGameObject (UnityEngine.Timeline.TrackAsset track, UnityEngine.Playables.PlayableDirector associatedDirector) (at E:/Setup/Unity 2019.3.0a4/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.timeline/Editor/Signals/SignalEmitterInspector.cs:372)
UnityEditor.Timeline.Signals.SignalEmitterInspector.UpdateState () (at E:/Setup/Unity 2019.3.0a4/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.timeline/Editor/Signals/SignalEmitterInspector.cs:148)
UnityEditor.Timeline.Signals.SignalEmitterInspector.OnEnable () (at E:/Setup/Unity 2019.3.0a4/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.timeline/Editor/Signals/SignalEmitterInspector.cs:72)
UnityEditor.Presets.PresetEditor:OnEnable()