fix in refX_unit initialization
fix in refX_unit initialization

bsipocz/pyspeckit,low-sky/pyspeckit,vlas-sokolov/pyspeckit,dinossimpson/pyspeckit,dinossimpson/pyspeckit,keflavich/pyspeckit,mikelum/pyspeckit,vlas-sokolov/pyspeckit,e-koch/pyspeckit,e-koch/pyspeckit,pyspeckit/pyspeckit,jpinedaf/pyspeckit,bsipocz/pyspeckit,low-sky/pyspeckit,pyspeckit/pyspeckit,allisony/pyspeckit,mikelum/pyspeckit,jpinedaf/pyspeckit,keflavich/pyspeckit,allisony/pyspeckit