Undefined variable: primary_local_tasks

I had the same issue (but not with skip_nav_class, that's an adaptive theme issue, not rubik or tao).

I got the notice to go away by enabling tao.

This isn't a bug, Rubik is a sub theme of Tao. If you enabled tao you download Tao (http://drupal.org/project/tao) you will no longer have this issue as Tao is what declares the "primary_local_tasks" variable for rubik to use.

I freshly installed the Rubik admin theme and Tao, and nearly the same error is being thrown:

Notice: Undefined variable: primary_local_tasks in include() (line 10 of /sites/all/themes/rubik/page.tpl.php).

(nothing about skip_nav_class)
To mention that I installed Tao after Rubik, after noticing the required dependancy. Before Tao installation, a lot of other errors showed up.
Could you please (re)check in this version?

You should clear all caches...

you shoud enable base theme Tao

I enabled tao, but was still getting the errors; I wrapped the two variables in isset() and it went away in my subtheme

for more context, here are the two lines in full:

<?php if (isset($primary_local_tasks)): ?><ul class="links clearfix"><?php print render($primary_local_tasks) ?></ul><?php endif; ?>

<?php if (isset($secondary_local_tasks)): ?><ul class="links clearfix"><?php print render($secondary_local_tasks) ?></ul><?php endif; ?>