fixed and tested NetcdfCFWriter when using a null LatLonRect llbb in mak...

fixed and tested NetcdfCFWriter when using a null LatLonRect llbb in makeFile method (e-support ITW-634910)

This fixes the case where the LatLonRectangle is set to null. This only works for NetcdfCFWriter.makeFile with the LatLonRectangle llbb signature, not the one with the ProjectionRect llbb in the signature. Will need to discuss changes to the ProjectionRect llbb signature, as this directly affects what is done in cdm 4.5.