[web/views] avoid propagation of NoSelectableObject in some case of inlined relations / permissions When selecting an inlined creation form, we should catch the NoSelectable exception that will be raised if the user cannot add entities of the target type (this is not and cannot be verified earlier) or if some other custom selector prevents the form from being selected. Closes #6510921

# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s precreate script, executed at instance creation time or when
the cube is added to an existing instance, before the schema is serialized.

This is typically to create groups referenced by the cube'schema.
"""