[FIX] website_event_sale: sell non-event tickets

- Create a ticket product.
- Add it to an event.
-  Uncheck it as ticket.
- Sell it on the website.

A traceback is raised here:
https://github.com/odoo/odoo/blob/88e32c5af9f47981bebea560de456a1404b4e382/addons/website_event_sale/models/sale_order.py#L88

It happens because a ticket is found, but `new_qty` is a `string` while
while `old_qty` is a `float`. It is coming from `add_qty` which is a
`string` while a `float` is expected.

We apply the same logic than:

https://github.com/odoo/odoo/blob/88e32c5af9f47981bebea560de456a1404b4e382/addons/website_sale/models/sale_order.py#L181-L190

opw-2347633

closes odoo/odoo#59216

X-original-commit: 859ffdbc3a80f50be9e298c0b5e86cd58eca0d89
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/website_event_sale/models/sale_order.py

@@ -53,6 +53,17 @@ class SaleOrder(models.Model):
     def _cart_update(self, product_id=None, line_id=None, add_qty=0, set_qty=0, **kwargs):
         OrderLine = self.env['sale.order.line']
 
+        try:
+            if add_qty:
+                add_qty = float(add_qty)
+        except ValueError:
+            add_qty = 1
+        try:
+            if set_qty:
+                set_qty = float(set_qty)
+        except ValueError:
+            set_qty = 0
+
         if line_id:
             line = OrderLine.browse(line_id)
             ticket = line.event_ticket_id