Use the correct startPos when repeating the search for 'endobj' operators in XRef.indexObjects (PR 9288 follow-up)

src/core/obj.js

@@ -1208,7 +1208,7 @@ var XRef = (function XRefClosure() {
                 break;
               }
             }
-            startPos += contentLength;
+            startPos = endPos;
           }
           let content = buffer.subarray(position, position + contentLength);