User have access to triggers which contain hosts with RW permission and Deny (no explicity set).

1. have systems with 2 hosts and user which has rw permissions to one host and no permissions to other.
2. create trigger which contain both hosts.
3. in configuration section this trigger will be seen by user and all fields except expression can be updated.
4. if user try to update expression field, error "Incorrect trigger expression. Host "0webh" does not exist or you have no access to this host. [CTrigger.update -> CTrigger.checkInput]" is shown.