Display outlines even if one has no title

Fixes #17856.

src/core/catalog.js

@@ -324,7 +324,7 @@ class Catalog {
         continue;
       }
       if (!outlineDict.has("Title")) {
-        throw new FormatError("Invalid outline item encountered.");
+        warn("Invalid outline item encountered.");
       }
 
       const data = { url: null, dest: null, action: null };
@@ -357,7 +357,7 @@ class Catalog {
         unsafeUrl: data.unsafeUrl,
         newWindow: data.newWindow,
         setOCGState: data.setOCGState,
-        title: stringToPDFString(title),
+        title: typeof title === "string" ? stringToPDFString(title) : "",
         color: rgbColor,
         count: Number.isInteger(count) ? count : undefined,
         bold: !!(flags & 2),

test/pdfs/issue17856.pdf.link

@@ -0,0 +1,2 @@
+https://github.com/mozilla/pdf.js/files/14808044/outline-without-title.pdf
+

test/test_manifest.json

@@ -9779,5 +9779,13 @@
     "rounds": 1,
     "link": true,
     "type": "eq"
+  },
+  {
+    "id": "issue17856",
+    "file": "pdfs/issue17856.pdf",
+    "md5": "b31e5258948f0f4bb99eb5d4127c2162",
+    "rounds": 1,
+    "link": true,
+    "type": "other"
   }
 ]

test/unit/api_spec.js

@@ -1719,6 +1719,36 @@ describe("api", function () {
       await loadingTask.destroy();
     });
 
+    it("gets outline, with missing title (issue 17856)", async function () {
+      if (isNodeJS) {
+        pending("Linked test-cases are not supported in Node.js.");
+      }
+      const loadingTask = getDocument(buildGetDocumentParams("issue17856.pdf"));
+      const pdfDoc = await loadingTask.promise;
+      const outline = await pdfDoc.getOutline();
+
+      expect(Array.isArray(outline)).toEqual(true);
+      expect(outline.length).toEqual(9);
+
+      expect(outline[0]).toEqual({
+        action: null,
+        attachment: undefined,
+        dest: "section.1",
+        url: null,
+        unsafeUrl: undefined,
+        newWindow: undefined,
+        setOCGState: undefined,
+        title: "",
+        color: new Uint8ClampedArray([0, 0, 0]),
+        count: undefined,
+        bold: false,
+        italic: false,
+        items: [],
+      });
+
+      await loadingTask.destroy();
+    });
+
     it("gets outline, with dest-strings using PDFDocEncoding (issue 14864)", async function () {
       if (isNodeJS) {
         pending("Linked test-cases are not supported in Node.js.");