"Create Template Document" trigger an not be set u

Hello, We want to create a "Create Template Document" trigger. Normally, we can choose if we want to use a "document template" or a "template picklist". We want to choose a "template picklist". Unfortunately, we can not save the trigger if we do not select a "document template". Indeed, this field is required (it is written in red color). Please, see the screenshot below. Thank you ! Matthieu