CSS styles not adding

[Filippo Bistaffa <filippo.bistaffa AT gmail.com>]

Hi to all, I have an issue using CSS styles. From what I've read in the documentation, the CSS styles should be cumulative, so if I do something like:

g.addAttribute("ui.stylesheet", "node { fill-color: green; }");

g.addAttribute("ui.stylesheet", "graph { fill-color: red; }");

I should see the background red AND the nodes green. Instead of the intended result, I only see the background red.

If I invert the order of the two instructions, I see the nodes green, but the background is in the default color. 

It seems that the styles are not merged, but the old one is completely discarded and the new one is applied.