Fixed bug when creating a new network, forgot to set Target. Caused seg fault...

Fixed bug when creating a new network, forgot to set Target.  Caused seg fault when creating new ground control point.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3014 41f8697f-d340-4b68-9986-7bafba869bb8