change the start values for the age moments for an empty system from undefined (which is appropriate) to a default of zero which works with the templates of the old bgc_md since they use the moment system which leads to scipy errors if Nan are encountered
change the start values for the age moments for an empty system from undefined (which is appropriate) to a default of zero which works with the templates of the old bgc_md since they use the moment system which leads to scipy errors if Nan are encountered

MPIBGC-TEE/CompartmentalSystems,MPIBGC-TEE/CompartmentalSystems,MPIBGC-TEE/CompartmentalSystems