[fptl] non-shadowcasting directional lights were turning the scene black

Assets/ScriptableRenderLoop/fptl/FptlLighting.cs

 					vy = worldToView.MultiplyVector(vy);
 					vz = worldToView.MultiplyVector(vz);
 
-					l.uShadowLightIndex = (uint)nLight;
+					l.uShadowLightIndex = (light.light.shadows != LightShadows.None) ? (uint)nLight : 0xffffffff;
 
 					l.vLaxisX = vx;
 					l.vLaxisY = vy;

Assets/ScriptableRenderLoop/fptl/Internal-DeferredShading.shader

 		DirectionalLight lightData = g_dirLightData[i];
 		float atten = 1;
 
-		float shadowScalar = SampleShadow(DIRECTIONAL_LIGHT, vPositionWs, 0, lightData.uShadowLightIndex);
-		atten *= shadowScalar;
+		[branch]
+		if (lightData.uShadowLightIndex != 0xffffffff)
+		{
+			float shadowScalar = SampleShadow(DIRECTIONAL_LIGHT, vPositionWs, 0, lightData.uShadowLightIndex);
+			atten *= shadowScalar;
+		}
 
 		UnityLight light;
 		light.color.xyz = lightData.vCol.xyz * atten;