How to reproduce:
1. Open the attached 'HdrpLights.zip' project
2. Open 'SampleScene' Scene
3. Select 'Particles System' in the Hierarchy
4. Notice that Lights option is checked of Particle System component in the Inspector

Expected result: Particles emit light in the Scene View
Actual result: Particles do not emit light in the Scene View

Reproducible with: 2019.2.0b8(6.5.2, 6.7.1), 2019.2.16f1(6.9.0, 6.9.2), 2019.3.0f2 (7.1.1, 7.1.5, 7.1.6), 2020.1.0a16 (7.1.1, 7.1.5, 7.1.6)
Not reproducible with: 2018.4.14f1(4.1.0- preview) 2019.2.0b7(6.5.2, 6.7.1)
Could not test with: 2017.4.35f1 HDRP is no introduced

Notes:
1. Video of reproduction attached in the Edit
2. Reproducible with DirectX11, DirectX12, Vulkan, Metal graphics API
3. Reproducible on macOS, Windows
4. Could not test player build since it builds a skybox only
5. Not reproducible with URP, built-in pipeline
6. Error is thrown to the Console when Ratio of Light setting is set in HDRP 7.1.5 and earlier: 'NullReferenceException: Object reference not set to an instance of an object
UnityEngine.Experimental.Rendering.HDPipeline.LightLoop.PrepareLightsForGPU (UnityEngine.Rendering.CommandBuffer cmd, UnityEngine.Experimental.Rendering.HDPipeline.HDCamera hdCamera, UnityEngine.Rendering.CullingResults cullResults, UnityEngine.Experimental.Rendering.HDPipeline.HDProbeCullingResults hdProbeCullingResults, UnityEngine.Experimental.Rendering.HDPipeline.DensityVolumeList densityVolumes, UnityEngine.Experimental.Rendering.HDPipeline.DebugDisplaySettings debugDisplaySettings, UnityEngine.Experimental.Rendering.HDPipeline.AOVRequestData aovRequest)'
- When Ratio of Light setting is set in HDRP 7.1.5 and earlier Game View turns black, Scene View grey if Ratio of Light is set in Particle System component