Custom PDF templates are not taken into account

Steps to reproduce:

• create a new PDF template (i.e. create a new page and select the PDF template page type)
• make some small change so that the generated PDF will be different than the one obtained with the default template
• go to the Wiki administration > Content > PDF Export and add the created template to the list of known templates
• go the the wiki page to export to PDF, and select the created template on the PDF Export Options modal

Expected results: the selected (custom) PDF template is used.
Actual results: the default PDF template is used instead.

Note that this issue is about the new client-side PDF export.