fix npe in the jung library

java.lang.NullPointerException
null
edu.uci.ics.jung.visualization.control.PickingGraphMousePlugin.mouseDragged(PickingGraphMousePlugin.java:286)
edu.uci.ics.jung.visualization.control.PluggableGraphMouse.mouseDragged(PluggableGraphMouse.java:133)
Merge branch 'master' into net-device
libvirt: add choices for network disk type
Merge branch 'net-device' into test