Fixed a bug when argsorting a single point.
Fixed a bug when argsorting a single point.

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