How to reproduce:
1. Open the attached project ("PlayableDirectorPerformance")
2. Open the Profiler and enable the Profile Editor
3. In Profiler, select the Hierarchy preview
4. In Profiler search field type PanelUpdate and press record
5. In Scene Hierarchy select the "PD" GameObject and clear the Playable field
6. Observe the Profiler Hierarchy

Expected result: the activity callbacks do not change
Actual result: extra PanelUpdate callbacks can be seen

Reproducible with Unity versions: 2018.4.3f1, 2018.4.5f1, 2019.1.12f1, 2019.1.13f1, 2019.2.0b6, 2019.2.0f1, 2019.3.0a5, 2019.3.0a11
Not reproducible with Unity versions: 2017.4.31f1, 2018.4.2f1, 2019.1.11f1, 2019.2.0b5, 2019.3.0a4

Reproducible with package versions: 1.0.0, 1.1.0

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QA: Here's an easier way to reproduce the bug.
Ensure that you are using internal mode in Unity. (Open the Unity About window (menu: Unity > About Unity...) and then type the word "internal". You should get a notification that says "Internal Mode On" (or "Internal Mode Off" if it was already on).

1) Create a new gameobject.
2) Open the timeline window.
3) Add a playable director to this new gameobject.

Result: The Timeline window is consistently repainted. This is show by the little colored dot at the top-left corner of the window. The colored dot changes color at each repaint. (See video)
Expected: The Timeline window should not be repainted. The colored dot should stay the same color.