From 01f7aa3d7941512721481110fdef9404dc3b0657 Mon Sep 17 00:00:00 2001
From: adrianhelvikspond <adrian.helvik@spond.com>
Date: Fri, 22 Mar 2024 11:00:05 +0100
Subject: [PATCH] Fix slice bug

---
 lib/program.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/program.js b/lib/program.js
index eeb060bc..6ccf2930 100644
--- a/lib/program.js
+++ b/lib/program.js
@@ -2540,7 +2540,9 @@ Program.prototype._attr = function(param, val) {
       , out = [];
 
     parts.forEach(function(part) {
-      part = self._attr(part, val).slice(2, -1);
+      var attr = self._attr(part, val);
+      if (attr == null) return;
+      part = attr.slice(2, -1);
       if (part === '') return;
       if (used[part]) return;
       used[part] = true;