Ensure that VSO Agent does not blow up on null BUILD_BUILDNUMBER
Ensure that VSO Agent does not blow up on null BUILD_BUILDNUMBER

ermshiperete/GitVersion,ParticularLabs/GitVersion,dazinator/GitVersion,asbjornu/GitVersion,GitTools/GitVersion,gep13/GitVersion,ermshiperete/GitVersion,ermshiperete/GitVersion,dazinator/GitVersion,ParticularLabs/GitVersion,gep13/GitVersion,asbjornu/GitVersion,ermshiperete/GitVersion,GitTools/GitVersion