Fixed _calculate_link_length for new numbering.
Fixed _calculate_link_length for new numbering.

SiccarPoint/landlab,csherwood-usgs/landlab,csherwood-usgs/landlab,landlab/landlab,ManuSchmi88/landlab,laijingtao/landlab,landlab/landlab,cmshobe/landlab,Carralex/landlab,landlab/landlab,cmshobe/landlab,amandersillinois/landlab,RondaStrauch/landlab,cmshobe/landlab,SiccarPoint/landlab,ManuSchmi88/landlab,laijingtao/landlab,RondaStrauch/landlab,Carralex/landlab,RondaStrauch/landlab,ManuSchmi88/landlab,Carralex/landlab,amandersillinois/landlab