correctly check if variable is empty
correctly check if variable is empty

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