fixed handling case with zero packages in setup.py
fixed handling case with zero packages in setup.py

ros/catkin,jack-oquin/catkin,wkentaro/catkin,thaddeustaylor/catkin,thaddeustaylor/catkin,shyamalschandra/catkin,wkentaro/catkin,shyamalschandra/catkin,beni55/catkin,wkentaro/catkin,beni55/catkin,thaddeustaylor/catkin,harmishhk/catkin,ros/catkin,asmodehn/catkin,asmodehn/catkin,shyamalschandra/catkin,jack-oquin/catkin,ros/catkin,harmishhk/catkin,meyerj/catkin,jack-oquin/catkin,meyerj/catkin,scpeters/catkin,harmishhk/catkin,meyerj/catkin,scpeters/catkin,asmodehn/catkin,beni55/catkin,scpeters/catkin