I'm pretty sure there's no class action litigation pending.
For one thing, the company would be obligated to disclose it in the 10-Q.
For another, the lawyers that file class actions like to do so with a splash, with a widely-distributed press release. Sometimes they announce plans to "investigate" even before they file.
Finally, there are a few places on the web where you can search for class actions. I just looked at a couple, and nothing came up.
Now, it would come as no surprise that they have received a shakedown letter or two to the bottom-feeders.
In the end, though, maybe the lack of a class action signifies the assessment of the plaintiffs' bar that there is a low chance of recovery on any claim that is successfully brought. The most successful plaintiffs' lawyers are the ones that are careful to choose the right cases, after all.