From bb14e5d66fab81e9a27327355c6f2e478b7b1d13 Mon Sep 17 00:00:00 2001
From: "mr. m" <91018726+mr-cheffy@users.noreply.github.com>
Date: Tue, 28 Apr 2026 00:49:18 +0200
Subject: [PATCH] no-bug: Make checks if boost css is undefined (gh-13451)

---
 src/zen/boosts/ZenBoostStyles.sys.mjs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/zen/boosts/ZenBoostStyles.sys.mjs b/src/zen/boosts/ZenBoostStyles.sys.mjs
index cc6ca22e5..40c230f6f 100644
--- a/src/zen/boosts/ZenBoostStyles.sys.mjs
+++ b/src/zen/boosts/ZenBoostStyles.sys.mjs
@@ -88,7 +88,7 @@ export class nsZenBoostStyles {
       style += `}\n`;
     }
 
-    if (boostData.customCSS.trim() != "") {
+    if ((boostData.customCSS || "").trim() != "") {
       style += `/* USER CSS */\n`;
       style += `${boostData.customCSS || ""}\n`;
     }