Don't call ne_get_node_cmap() if there is nothing to get.
Don't call ne_get_node_cmap() if there is nothing to get.

I thought Nemesis handled this correctly when you passed NULL pointers
for the data vectors, but apparently it throws an error.

Refs #1087.

hrittich/libmesh,pbauman/libmesh,balborian/libmesh,giorgiobornia/libmesh,friedmud/libmesh,svallaghe/libmesh,BalticPinguin/libmesh,pbauman/libmesh,90jrong/libmesh,friedmud/libmesh,friedmud/libmesh,balborian/libmesh,vikramvgarg/libmesh,hrittich/libmesh,capitalaslash/libmesh,libMesh/libmesh,90jrong/libmesh,90jrong/libmesh,roystgnr/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,giorgiobornia/libmesh,roystgnr/libmesh,roystgnr/libmesh,balborian/libmesh,dschwen/libmesh,dschwen/libmesh,balborian/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,90jrong/libmesh,pbauman/libmesh,svallaghe/libmesh,dschwen/libmesh,vikramvgarg/libmesh,hrittich/libmesh,svallaghe/libmesh,vikramvgarg/libmesh,pbauman/libmesh,BalticPinguin/libmesh,benkirk/libmesh,giorgiobornia/libmesh,vikramvgarg/libmesh,giorgiobornia/libmesh,friedmud/libmesh,benkirk/libmesh,hrittich/libmesh,svallaghe/libmesh,pbauman/libmesh,vikramvgarg/libmesh,friedmud/libmesh,libMesh/libmesh,BalticPinguin/libmesh,benkirk/libmesh,jwpeterson/libmesh,90jrong/libmesh,vikramvgarg/libmesh,libMesh/libmesh,hrittich/libmesh,roystgnr/libmesh,benkirk/libmesh,90jrong/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,benkirk/libmesh,capitalaslash/libmesh,svallaghe/libmesh,vikramvgarg/libmesh,balborian/libmesh,dschwen/libmesh,hrittich/libmesh,pbauman/libmesh,hrittich/libmesh,90jrong/libmesh,hrittich/libmesh,capitalaslash/libmesh,vikramvgarg/libmesh,svallaghe/libmesh,roystgnr/libmesh,giorgiobornia/libmesh,90jrong/libmesh,benkirk/libmesh,friedmud/libmesh,balborian/libmesh,BalticPinguin/libmesh,friedmud/libmesh,hrittich/libmesh,capitalaslash/libmesh,giorgiobornia/libmesh,90jrong/libmesh,giorgiobornia/libmesh,benkirk/libmesh,BalticPinguin/libmesh,dschwen/libmesh,capitalaslash/libmesh,friedmud/libmesh,svallaghe/libmesh,giorgiobornia/libmesh,jwpeterson/libmesh,pbauman/libmesh,BalticPinguin/libmesh,svallaghe/libmesh,svallaghe/libmesh,balborian/libmesh,balborian/libmesh,pbauman/libmesh,vikramvgarg/libmesh,libMesh/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,balborian/libmesh,dschwen/libmesh,pbauman/libmesh,friedmud/libmesh,libMesh/libmesh,benkirk/libmesh,roystgnr/libmesh,roystgnr/libmesh,balborian/libmesh,benkirk/libmesh,libMesh/libmesh,capitalaslash/libmesh,giorgiobornia/libmesh,jwpeterson/libmesh,libMesh/libmesh,roystgnr/libmesh,BalticPinguin/libmesh