How to reproduce:

• Add a restriction on a content's attribute
  • Make a right restriction
  • Let the right id empty
  • Example: 

<restrict-to>
    <right read-write-direction="write" id="" />
 </restrict-to>

• Try to create a content of this type
  • An error occurs because the RightManager can't deal with this empty right id

The application should fail earlier, while parsing the restriction, not while trying to use it.