[FIX] base: don't assume res_ids is a list

https://github.com/odoo/odoo/pull/85150 introduced the method
_render_qweb_pdf_prepare_streams called from _render_qweb_pdf
giving it its res_ids.
Two places in this method are assuming res_ids will be a list, but
it is not always the case. Plenty of call to _render_qweb_pdf is
giving it a single id as a parameter.

This will ensure that res_ids is a list by creating one for single ids
too before proceeding with the logic of the pdf rendering.

closes odoo/odoo#91631

Signed-off-by: Laurent Smet <las@odoo.com>

odoo/addons/base/models/ir_actions_report.py

@@ -764,6 +764,8 @@ class IrActionsReport(models.Model):
         self.ensure_one()
         if not data:
             data = {}
+        if isinstance(res_ids, int):
+            res_ids = [res_ids]
         data.setdefault('report_type', 'pdf')
         self_sudo = self.sudo()