compileFilterRules checked only pol.ACLs == nil to decide whether
to return FilterAllowAll (permit-any). Policies that use only Grants
(no ACLs) had nil ACLs, so the function short-circuited before
compiling any CapGrant rules. This meant cap/relay, cap/drive, and
any other App-based grant capabilities were silently ignored.
Check both ACLs and Grants are empty before returning FilterAllowAll.
Updates #2180