[FIX] website_payment: handle an error for empty donation amount

When a user pays a donation with an empty amount value, the system
passes this value as an empty string, which is leading to a type-casting error
because an empty string cannot be directly converted to a numerical value like
a float.

Error: `ValueError: could not convert string to float: `

To handle this situation, we should use '_cast_as_int' and
'_cast_as_float' methods because these methods provide try-except blocks,
effectively handling these types of errors. This ensures that when an empty
amount value is encountered, the system manages the error.

sentry-4376573159

closes odoo/odoo#134026

X-original-commit: cae9f647b9e032aedfccc528d124acc639ecbf7f
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

addons/website_payment/controllers/portal.py

@@ -23,8 +23,8 @@ class PaymentPortal(payment_portal.PaymentPortal):
         :raise: werkzeug.exceptions.NotFound if the access token is invalid
         """
         kwargs['is_donation'] = True
-        kwargs['currency_id'] = int(kwargs.get('currency_id', request.env.company.currency_id.id))
-        kwargs['amount'] = float(kwargs.get('amount', 25))
+        kwargs['currency_id'] = self._cast_as_int(kwargs.get('currency_id')) or request.env.company.currency_id.id
+        kwargs['amount'] = self._cast_as_float(kwargs.get('amount')) or 25.0
         kwargs['donation_options'] = kwargs.get('donation_options', json_safe.dumps(dict(customAmount="freeAmount")))
 
         if request.env.user._is_public():