Undefined index: table_tools in template_preprocess_datatables_view()

For get rid of the annoying message just check if the array element exists:

  // Enable TableTools plugin support, if necessary.
  if (isset($options['elements']['table_tools']) && $options['elements']['table_tools']) {

Using 7.x-1.x-dev cannot reproduce it. Please try it with dev version and re-open the issue if you still have this problem.

This is easy to reproduce, use clean drupal install.

@formatC'vt

You should know that all new code will be made into dev-versions of modules, i.e. 7.x-1.x-dev. Please install the dev version, not 7.x-1.2, and you'll see that the issue is not there.

If you still see the issue, then provide a new patch, since your patch doesn't apply to the dev version.

@formatC'vt

I'm sorry, you're right. The issue is still there. I was on the master branch, not on dev, that's why I couldn't reproduce it at the first time.
I'll check your patch as soon as I got more time (give me 2 days) and I'll commit it if it works.

I've a little improved the patch, reducing the redundant check.

Since this is a trivial check, I've just pushed the patch to the dev-Version.

Thanks @Ranieri Machado and @formatC'vt.

#8 worked for me.

Thanks!