Pages with children cannot be exported to PDF anymore using "&includechilds="

STEPS TO REPRODUCE

1. Create the following page structure: P1/P2/P3/
2. Add some (distinctive) content on each page
3. Export P1 with children pages to PDF using:

   <server>/bin/export/P1/WebHome?format=pdf&pdfcover=1&pdfcover=0&pdftoc=1&pdftoc=0&pdfheader=1&pdfheader=0&pdffooter=1&pdffooter=0&includechilds=2

EXPECTED RESULTS

The PDF is exported successfully and includes the content of P1 and its children: P2 and P3.

ACTUAL RESULTS

Only the content of P1 page is displayed in the exported PDF.

The issue could not be reproduced on XWiki 13.3 or XWiki 12.10.7.