From d5e14d3dc33cbbd65f8441551fb4feaf072a0cbd Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Tue, 3 Aug 2021 15:50:25 +0200
Subject: [PATCH] Prevent breaking errors when an optional content group is
 undefined (issue 13851)

In the referenced PDF document *most* of the form `/Form` XObjects don't have an `/OC` entry, which thus causes the runtime failure during rendering.
---
 src/display/optional_content_config.js | 4 ++++
 test/pdfs/issue13851.pdf.link          | 1 +
 test/test_manifest.json                | 7 +++++++
 3 files changed, 12 insertions(+)
 create mode 100644 test/pdfs/issue13851.pdf.link

diff --git a/src/display/optional_content_config.js b/src/display/optional_content_config.js
index 424c3a5c6..b50379efb 100644
--- a/src/display/optional_content_config.js
+++ b/src/display/optional_content_config.js
@@ -95,6 +95,10 @@ class OptionalContentConfig {
   }
 
   isVisible(group) {
+    if (!group) {
+      warn("Optional content group not defined.");
+      return true;
+    }
     if (group.type === "OCG") {
       if (!this._groups.has(group.id)) {
         warn(`Optional content group not found: ${group.id}`);
diff --git a/test/pdfs/issue13851.pdf.link b/test/pdfs/issue13851.pdf.link
new file mode 100644
index 000000000..c035814ac
--- /dev/null
+++ b/test/pdfs/issue13851.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/6896539/doc_image.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 9c2325b4c..79c2e0297 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -3688,6 +3688,13 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue13851",
+       "file": "pdfs/issue13851.pdf",
+       "md5": "d933d397c4efc80faba856bf8deafc1a",
+       "rounds": 1,
+       "link": true,
+       "type": "eq"
+    },
     {  "id": "issue1655",
        "file": "pdfs/issue1655r.pdf",
        "md5": "569f48449ba57c15c4f9ade151a651c5",