Fixed compiler error
Fixed compiler error

This code should never have used NULL, but checked for 0 as it is not
dealing with pointers.

Change-Id: If0247a2a00c0bcdcecd3df5573a0df8a7746f2bb

ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs