Currently, when the user enters a value of `VAT` like '/' or any single character, an error occurs. Error: "IndexError: string index out of range" This is because the recently applied PR [1] added a Line [1] that tries to access the second digit of VAT, but the user added only one character. This commit fixes the above issue by accessing the second character when the length of the VAT is more than one character. PR [1]-https://github.com/odoo/odoo/pull/136146 Line [1]-https://github.com/odoo/odoo/blob/422625615b2f6708667fa44d2a9e83ad3e66e5af/addons/base_vat/models/res_partner.py#L92 sentry-4524865338 closes odoo/odoo#138454 X-original-commit: 57f59f2088c46f4603ff83bbcf2db42d705331fe Signed-off-by: Olivier Colson (oco) <oco@odoo.com> Signed-off-by: ANSARI MAHAMADASIF (maan) <maan@odoo.com>