Missing test on files variable in send method of ir.email
In the send() method of ir.email, variable 'files' has None as default value but there's a loop on 'files' (https://foss.heptapod.net/tryton/tryton/-/blob/d54a460a5567b1f12d57df0ee095c24fa02a98aa/trytond/trytond/ir/email_.py#L193) in the method which raise a TypeError: 'NoneType' object is not iterable.
Edited by Maxime Richez