From 742a7cd4300144cd213182e4b2a9b19dae8588c1 Mon Sep 17 00:00:00 2001
From: Richard Hansen <rhansen@rhansen.org>
Date: Fri, 19 Mar 2021 15:49:33 -0400
Subject: [PATCH] cssmanager: Throw if no matching style sheet is found

This avoids a later null dereference when the stack trace isn't as
useful.
---
 src/static/js/cssmanager.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/static/js/cssmanager.js b/src/static/js/cssmanager.js
index 9d6f277e..b7af85d4 100644
--- a/src/static/js/cssmanager.js
+++ b/src/static/js/cssmanager.js
@@ -43,7 +43,9 @@ const makeCSSManager = (emptyStylesheetTitle, doc) => {
     for (const s of win.document.styleSheets) {
       if (s.title === title) return s;
     }
-    return null;
+    const err = new Error(`no sheet with title ${title} in doc ${doc}`)
+    console.error(err);
+    throw err;
   };
 
   const browserSheet = getSheetByTitle(emptyStylesheetTitle);