From ca43ac369faafd408ebf2f9df1c51f3cf27c52f3 Mon Sep 17 00:00:00 2001
From: Stewart Allen <stewart.allen@gmail.com>
Date: Thu, 19 Nov 2020 11:10:49 -0500
Subject: [PATCH] handle empty shells

---
 src/kiri/slice.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/kiri/slice.js b/src/kiri/slice.js
index ef4f0d69..cb21c485 100644
--- a/src/kiri/slice.js
+++ b/src/kiri/slice.js
@@ -76,7 +76,7 @@
      * @returns {Polygon[]} array of top polygons
      */
     Top.prototype.shellsAtDepth = function(depth) {
-        return this.shells.filter(poly => poly.depth === depth);
+        return this.shells ? this.shells.filter(poly => poly.depth === depth) : [];
     };
 
     /** ******************************************************************