Here's a link that explains how to go back and forth from the nightlies (beta) and the stable version:

Start by uninstalling the nightly version
sudo apt-get install ppa-purge
sudo ppa-purge ppa:mutlaqja/indinightly

Then you may or may not need to reinstall the stable version:
sudo apt-add-repository ppa:mutlaqja/indinightly
sudo apt-get update
sudo apt-get install indi-full kstars-bleeding gsc

Good luck!