[FIX] l10n_fr_pos_cert: default timezone

When mocking views, if there is no timezone set in context and for user,
providing Boolean value to pytz.timezone() functions results in error.
It doesn't happen in UI as UI takes value from session timezone.

closes odoo/odoo#112151

X-original-commit: 694de9d94de105336398a259c77d7e5bb0e42438
Signed-off-by: William André (wan) <wan@odoo.com>

addons/l10n_fr_pos_cert/models/res_company.py

@@ -11,7 +11,7 @@ import pytz
 def ctx_tz(record, field):
     res_lang = None
     ctx = record._context
-    tz_name = pytz.timezone(ctx.get('tz') or record.env.user.tz)
+    tz_name = pytz.timezone(ctx.get('tz') or record.env.user.tz or 'UTC')
     timestamp = Datetime.from_string(record[field])
     if ctx.get('lang'):
         res_lang = record.env['res.lang']._lang_get(ctx['lang'])