Added fix for Particle Spotlights in the light loop

Fixed default particle shader to be correct Unilit/Fade

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

                 // SdotL * invAngleRange + (-cosOuterAngle * invAngleRange)
                 // If we precompute the terms in a MAD instruction
                 float cosOuterAngle = Mathf.Cos(Mathf.Deg2Rad * lightData.spotAngle * 0.5f);
-                float cosInneAngle = Mathf.Cos(LightmapperUtils.ExtractInnerCone(lightData.light) * 0.5f);
+                // We neeed to do a null check for particle lights
+                // This should be changed in the future
+                // Particle lights will use an inline function
+                float cosInneAngle;
+                if (lightData.light != null)
+                {
+                    cosInneAngle = Mathf.Cos(LightmapperUtils.ExtractInnerCone(lightData.light) * 0.5f);
+                }
+                else
+                {
+                    cosInneAngle = Mathf.Cos((2.0f * Mathf.Atan(Mathf.Tan(lightData.spotAngle * 0.5f * Mathf.Deg2Rad) * (64.0f - 18.0f) / 64.0f)) * 0.5f);
+                }
                 float smoothAngleRange = Mathf.Max(0.001f, cosInneAngle - cosOuterAngle);
                 float invAngleRange = 1.0f / smoothAngleRange;
                 float add = -cosOuterAngle * invAngleRange;

ScriptableRenderPipeline/LightweightPipeline/LWRP/Materials/Lightweight-DefaultParticle.mat

   m_PrefabParentObject: {fileID: 0}
   m_PrefabInternal: {fileID: 0}
   m_Name: Lightweight-DefaultParticle
-  m_Shader: {fileID: 4800000, guid: b7839dad95683814aa64166edc107ae2, type: 3}
-  m_ShaderKeywords: 
+  m_Shader: {fileID: 4800000, guid: 0406db5a14f94604a8c57ccfbc9f3b46, type: 3}
+  m_ShaderKeywords: _ALPHABLEND_ON
-  m_CustomRenderQueue: -1
-  stringTagMap: {}
+  m_CustomRenderQueue: 3000
+  stringTagMap:
+    RenderType: Transparent
   disabledShaderPasses:
   - ALWAYS
   m_SavedProperties:
     - _CameraFadingEnabled: 0
     - _CameraFarFadeDistance: 2
     - _CameraNearFadeDistance: 1
+    - _ColorMode: 0
     - _Cull: 2
     - _Cutoff: 0.5
     - _DetailNormalMapScale: 1
     - _DistortionStrengthScaled: 0
-    - _DstBlend: 0
+    - _DstBlend: 10
     - _EmissionEnabled: 0
     - _FlipbookMode: 0
     - _GlossMapScale: 1
-    - _LightingEnabled: 1
+    - _LightingEnabled: 0
-    - _Mode: 0
+    - _Mode: 2
     - _OcclusionStrength: 1
     - _Parallax: 0.02
     - _SmoothnessTextureChannel: 0
     - _SpecularHighlights: 1
-    - _SrcBlend: 1
+    - _SrcBlend: 5
-    - _ZWrite: 1
+    - _ZWrite: 0
+    - _ColorAddSubDiff: {r: 0, g: 0, b: 0, a: 0}
     - _EmissionColor: {r: 0, g: 0, b: 0, a: 1}
     - _SoftParticleFadeParams: {r: 0, g: 0, b: 0, a: 0}