Importing document view XML that contains checked-in nodes produces assertion error

Importing a document view XML of a repository which contains checked-in nodes, raises an AssertionError in

    public NodeKey( String key ) {
        assert key != null;
    -->    assert key.length() > IDENTIFIER_START_INDEX;
        this.key = key;
    }

The reason is that in some cases, the jcr:predecessors property can be empty (for example when a node is checked in)