twitter/bootstrap — pull request #6064 by thepeg (2012-11-29 11:49:36+00:00)
Title: Dropdown Touch Bug Fix

On touch device you are able to open a drop down but not to select a value inside it!

This line fix the problem and here you can read about this error and it's solution:
http://movableapp.com/2012/11/twitter-bootstrap-dropdown-bugfix