NSS gets confused when there are separate default and accessTo blocks

[RubenVerborgh]

As described in inrupt/solid-client-js#1035

[bourgeoa]

See comments on inrupt/solid-client-js#1035
Not having much information on the acl that created the bug, it seems related to having acl:default in a non container acl

Among an acl isValid function, NSS may check that :

• creating an acl for document (non-container resource) with PUT do not contain an acl:default.
• other points could include :
  • exist an acl: authorization, acl.mode, acl:accessTo
  • container acl has a Control
  • subject with acl:mode has an agentType (agent, group, evryone, logged agent, ...)