How to reproduce:
1. Open the attached project ("Repro.zip")
2. Open the "SampleScene" scene and observe that the lights are not working
3. In the Project Window search bar type in "LWRP-HighQuality" and click on it
4. In the Inspector Window tick the "Lighting" -> "Main Light" -> "Cast Shadows" option
5. Observe the Scene View again

Expected result: Spotlight and Point Light lights are visible when the cast shadows option is disabled
Actual result: Spotlight and Point Light lights don't work when both Main Light and Additional Light shadows are disabled

Reproduced with: LWRP - 4.0.0; LWRP - 4.0.1
Not reproducible: LWRP - 3.3.0; LWRP - 3.1.0