fix two corner cases where we dont have points

cuda_rasterizer/rasterizer_impl.cu

@@ -132,9 +132,9 @@ __global__ void identifyTileRanges(int L, uint64_t* point_list_keys, uint2* rang
 			ranges[prevtile].y = idx;
 			ranges[currtile].x = idx;
 		}
+	}
 	if (idx == L - 1)
 		ranges[currtile].y = L;
-	}
 }
 
 // Mark Gaussians as visible/invisible, based on view frustum testing
@@ -310,6 +310,7 @@ int CudaRasterizer::Rasterizer::forward(
 	cudaMemset(imgState.ranges, 0, tile_grid.x * tile_grid.y * sizeof(uint2));
 
 	// Identify start and end of per-tile workloads in sorted list
+	if (num_rendered > 0)
 		identifyTileRanges << <(num_rendered + 255) / 256, 256 >> > (
 			num_rendered,
 			binningState.point_list_keys,