Brunel 2.6 ---- Drop lines to the axises stopped working

[cjiang-ibm]

You can see the problem from
http://brunelvis.mybluemix.net/try.html

1. Use default data;

2. Paste this syntax:

   x(weight) y(mpg) color(origin) tooltip(#all) axes(x:grid, y:grid) interaction(call:'BrunelD3.crosshairs':mouseover)

3. Click build and hover over any dot

4. There is no drop lines.