Merge pull request #926 from Unity-Technologies/Branch_FixSkyReflectionSunReset

- Fixed Sky Reflection bad behavior when having no light in the scene…

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/DebugDisplayLatlong.shader

     {
         Pass
         {
-            ZWrite Off
+            ZWrite On
             ZTest Always
             Blend Off
             Cull Off

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoop.cs

 
                 Vector3 camPosWS = camera.transform.position;
 
+                // We need to properly reset this here otherwise if we go from 1 light to no visible light we would keep the old reference active.
+                m_CurrentSunLight = null;
+                m_CurrentSunLightShadowIndex = -1;
+
                 // Note: Light with null intensity/Color are culled by the C++, no need to test it here
                 if (cullResults.visibleLights.Count != 0 || cullResults.visibleReflectionProbes.Count != 0)
                 {
                     // will be use...)
                     // The lightLoop is in charge, not the shadow pass.
                     // For now we will still apply the maximum of shadow here but we don't apply the sorting by priority + slot allocation yet
-                    m_CurrentSunLight = null;
-                    m_CurrentSunLightShadowIndex = -1;
 
                     // 2. Go through all lights, convert them to GPU format.
                     // Create simultaneously data for culling (LigthVolumeData and rendering)