Fix OTS issue with empty index (#15289)

src/core/cff_parser.js

@@ -1864,10 +1864,9 @@ class CFFCompiler {
     // First 2 bytes contains the number of objects contained into this index
     const count = objects.length;
 
-    // If there is no object, just create an index. This technically
+    // If there is no object, just create an index.
-    // should just be [0, 0] but OTS has an issue with that.
     if (count === 0) {
-      return [0, 0, 0];
+      return [0, 0];
     }
 
     const data = [(count >> 8) & 0xff, count & 0xff];

test/pdfs/issue15289.pdf.link

@@ -0,0 +1,2 @@
+https://github.com/mozilla/pdf.js/files/9280755/issue15289.pdf
+

test/test_manifest.json

@@ -6882,5 +6882,14 @@
    "md5": "8505033d63625dfd77e90a3722b0c316",
    "rounds": 1,
    "type": "eq"
+   },
+   {  "id": "issue15289",
+      "file": "pdfs/issue15289.pdf",
+      "md5": "f3d20aee398e052ac3dce7cc030f50de",
+      "link": true,
+      "rounds": 1,
+      "firstPage": 1,
+      "lastPage": 1,
+      "type": "eq"
    }
 ]