fixing bug in delplot() reported by Alexander Fargus
fixing bug in delplot() reported by Alexander Fargus

tommy-u/chaco,ContinuumIO/chaco,ContinuumIO/chaco,ContinuumIO/chaco,ContinuumIO/chaco,burnpanck/chaco,burnpanck/chaco,tommy-u/chaco,burnpanck/chaco,tommy-u/chaco