Sitecore WFFM - Add to Contact List save action not showing contact lists

Environment: Sitecore 8.0 rev 150621

Sometimes when working with the WFFM on Sitecore you might experience the following issue with the 'Add the contact to contact list' save action.

This is because of following:
1. You have no lists created.
2. You have lists but it is not visible in the List Manager.

To ensure this go to the 'List Manager'/

In my case, I have list created but my List Manager won't show me anything.

In this case, go to the Sitecore Control Panel and Select the 'Indexing manager' under the 'Indexing' section.
Select the 'sitecore_list_index' as bellow image.

Then click 'Rebuild'

After it is done, visit the 'List Manager' again. If you have created some list earlier, it must appear in here now as bellow.

Then go to your form's save actions. Select the 'Add to Contact List' save action. Go to Edit.
Then you can see your lists are appear on that save action.