more robust and avoid file operations when arguments are empty
more robust and avoid file operations when arguments are empty

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