Merge pull request #13766 from Snuffleupagus/issue-13751

XFA - Handle `startIndex` correctly in the `Template.$toHTML` method (issue 13751)

src/core/xfa/template.js

@@ -5288,13 +5288,14 @@ class Template extends XFAObject {
           } else if (target instanceof ContentArea) {
             const index = contentAreas.findIndex(e => e === target);
             if (index !== -1) {
+              // In the next loop iteration `i` will be incremented, note the
+              // `continue` just below, hence we need to subtract one here.
               i = index - 1;
             } else {
               targetPageArea = target[$getParent]();
-              startIndex =
-                targetPageArea.contentArea.children.findIndex(
-                  e => e === target
-                ) - 1;
+              startIndex = targetPageArea.contentArea.children.findIndex(
+                e => e === target
+              );
             }
           }
           continue;

test/pdfs/issue13751.pdf.link

@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/6834770/Oswiadczenie_o_statusie_FATCA_i_CRS-1.pdf

test/test_manifest.json

@@ -1365,6 +1365,15 @@
        "enableXfa": true,
        "type": "eq"
     },
+    {  "id": "issue13751",
+       "file": "pdfs/issue13751.pdf",
+       "md5": "b9960bfa99be3573d9c32a9d55e5b7da",
+       "link": true,
+       "rounds": 1,
+       "lastPage": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "issue13756",
        "file": "pdfs/issue13756.pdf",
        "md5": "67040c6df3b5039fcbc81bf63b7c7f98",