Branch off Branch does not work

[rbrad8158]

Based on the documentation, this structure should work but the rendering fails with a 'NaN' for the x value. node_2_branch_1_branch_1 and node_2_branch_2_branch_1 will not render:
{ "nodes": [ { "nodeId": "node_2", "nodes": [ [{ "nodeId": "node_2_branch_1", "nodes": [ [{ "nodeId": "node_2_branch_1_branch_1", }], [{ "nodeId": "node_2_branch_2_branch_1", }] ] }], [{ "nodeId": "node_2_branch_2", }] ]}, { "nodeId": "node_999", "title": "Future", "date": "2012/12/20 00:00:00", "percent": 95, "description": "The last node of the time-line. The detail board will be on the left of mouse.", "lines": { "type": "dotted", "stroke_dasharray": "20, 10" } } ] }