Fixed crash when trying to access lights created in the light particle module.

ScriptableRenderPipeline/LightweightPipeline/LightweightPipeline.cs

             if (m_Asset.AreShadowsEnabled() && lightData.mainLightIndex != -1)
             {
                 VisibleLight mainLight = visibleLights[lightData.mainLightIndex];
+
+                    if (!LightweightUtils.IsSupportedShadowType(mainLight.lightType))
+                    {
+                        Debug.LogWarning("Only directional and spot shadows are supported by LightweightPipeline.");
+                        return;
+                    }
+
                     // There's no way to map shadow light indices. We need to pass in the original unsorted index.
                     // If no additional lights then no light sorting is performed and the indices match.
                     int shadowOriginalIndex = (lightData.hasAdditionalLights) ? GetLightUnsortedIndex(lightData.mainLightIndex) : lightData.mainLightIndex;
 
             Dictionary<int, int> visibleLightsIDMap = new Dictionary<int, int>();
             for (int i = 0; i < totalVisibleLights; ++i)
-                visibleLightsIDMap.Add(visibleLights[i].light.GetInstanceID(), i);
+                visibleLightsIDMap.Add(visibleLights[i].GetHashCode(), i);
 
             // Sorts light so we have all directionals first, then local lights.
             // Directionals are sorted further by shadow, cookie and intensity
 
             for (int i = 0; i < totalVisibleLights; ++i)
-                m_SortedLightIndexMap.Add(visibleLightsIDMap[visibleLights[i].light.GetInstanceID()]);
+                m_SortedLightIndexMap.Add(visibleLightsIDMap[visibleLights[i].GetHashCode()]);
 
             return GetMainLight(visibleLights);
         }
         {
             Vector3 shadowLightDir = Vector3.Normalize(shadowLight.localToWorld.GetColumn(2));
 
-            float bias = shadowLight.light.shadowBias * 0.1f;
-            float normalBias = shadowLight.light.shadowNormalBias;
+            Light light = shadowLight.light;
+            float bias = light.shadowBias * 0.1f;
+            float normalBias = light.shadowNormalBias;
             float shadowResolution = m_ShadowSlices[0].shadowResolution;
 
             const int maxShadowCascades = 4;

ScriptableRenderPipeline/LightweightPipeline/LightweightPipelineUtils.cs

                 if (rhs.lightType == LightType.Directional) return 1;
             }
 
+            // Particle Lights have the Light reference set to null
+            // They are at the end of the priority
+            if (lhsLight == null) return 1;
+            if (rhsLight == null) return -1;
+
             // In the following priority: Soft, Hard, None
             if (lhsLight.shadows != rhsLight.shadows)
                 return (int)rhsLight.shadows - (int)lhsLight.shadows;