KeyError when creating an attribute.group with no attribute.locations

[arthru]

When using the base_custom_attributes module, if you want to create an attribute.group with no attribute.location in the group, the operation fails with a KeyError.

The use case is creating a group now in order to full it with locations later. For example, in prestashoperpconnect, when I import product combination, I need to create the group when importing the product and to create attribute.locations when importing the combination.