test the behavior of empty catalogs in matching functions
test the behavior of empty catalogs in matching functions

DougBurke/astropy,StuartLittlefair/astropy,MSeifert04/astropy,dhomeier/astropy,dhomeier/astropy,astropy/astropy,stargaser/astropy,tbabej/astropy,kelle/astropy,tbabej/astropy,DougBurke/astropy,mhvk/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,saimn/astropy,AustereCuriosity/astropy,lpsinger/astropy,funbaker/astropy,astropy/astropy,mhvk/astropy,kelle/astropy,saimn/astropy,funbaker/astropy,aleksandr-bakanov/astropy,tbabej/astropy,mhvk/astropy,larrybradley/astropy,tbabej/astropy,funbaker/astropy,mhvk/astropy,larrybradley/astropy,AustereCuriosity/astropy,AustereCuriosity/astropy,joergdietrich/astropy,joergdietrich/astropy,bsipocz/astropy,tbabej/astropy,dhomeier/astropy,larrybradley/astropy,bsipocz/astropy,mhvk/astropy,DougBurke/astropy,joergdietrich/astropy,kelle/astropy,kelle/astropy,funbaker/astropy,MSeifert04/astropy,larrybradley/astropy,StuartLittlefair/astropy,saimn/astropy,stargaser/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,pllim/astropy,lpsinger/astropy,StuartLittlefair/astropy,joergdietrich/astropy,kelle/astropy,dhomeier/astropy,lpsinger/astropy,stargaser/astropy,astropy/astropy,AustereCuriosity/astropy,AustereCuriosity/astropy,lpsinger/astropy,MSeifert04/astropy,saimn/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,astropy/astropy,joergdietrich/astropy,pllim/astropy,saimn/astropy,stargaser/astropy,pllim/astropy,bsipocz/astropy,StuartLittlefair/astropy,lpsinger/astropy,StuartLittlefair/astropy,DougBurke/astropy,pllim/astropy,pllim/astropy,MSeifert04/astropy,astropy/astropy