Repro steps for 2017.2.0a1:

1. Open provided projects "test" scene
2. In the project window click on "boomfountain" located in "Assets" -> "Materials" -> "test"
3. Scroll up and down repeatedly in the inspector window, until the "Lighting" tabs "Ambient Color" changes to black

Repro steps for 2017.1.0b6:

1. Open provided projects "test" scene
2. In the project window click on "boomfountain" located in "Assets" -> "Materials" -> "test"
3. In the Lighting window click "Generate Lighting"
4. Repeatedly click on Inspector window tab and Lighting window tab until the "Lighting" tabs "Ambient Color" changes to black

Expected result: 2017.2.0a1) Nothing should happen as you're simply scrolling up and down in the Inspector window
2017.1.0b6) The lighting should be generated, by pressing the "Generate Lighting" button
Actual result: The "Lighting" windows "Ambient Color" changes to Black

Reproduced with: 2017.1.0b6, 2017.2.0a1
Regression introduced in: 2017.1.0b6
Did not reproduce on: 5.6.1p1

Note:
Added videos of repro