ARXML: return the unit and the comments even if a compu-method does not have a category
ARXML: return the unit and the comments even if a compu-method does not have a category

thanks to [at]H4rryK4ne for the catch.

Signed-off-by: Andreas Lauser <429495c8e182c230dc2e2e45b7683abab22a535c@mbition.io>

cantools/cantools,eerimoq/cantools