Invalid or illegal string output

        var tljson = {
            events: [
                {
                    start_date: {
                        month: "6",
                        year: "1997"
                    },
                    text: {
                        headline: "Started US Army basic training",
                        text:""
                    }
                }
            ]
        };
        new TL.Timeline('timeline', tljson);

Produces output that says SyntaxError: An invalid or illegal string was specified

Start by running the reported TL.Timeline example in the TimelineJS3 project and trace the source of the SyntaxError. No source file or test is named in the issue; done means this timeline data initializes without producing the invalid-or-illegal-string error.