Fix biweight_midcovariance for constant array
Fix biweight_midcovariance for constant array

mhvk/astropy,larrybradley/astropy,bsipocz/astropy,pllim/astropy,lpsinger/astropy,pllim/astropy,saimn/astropy,stargaser/astropy,pllim/astropy,astropy/astropy,StuartLittlefair/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,larrybradley/astropy,dhomeier/astropy,stargaser/astropy,dhomeier/astropy,dhomeier/astropy,StuartLittlefair/astropy,saimn/astropy,mhvk/astropy,lpsinger/astropy,pllim/astropy,lpsinger/astropy,pllim/astropy,astropy/astropy,mhvk/astropy,dhomeier/astropy,bsipocz/astropy,astropy/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,dhomeier/astropy,saimn/astropy,MSeifert04/astropy,bsipocz/astropy,StuartLittlefair/astropy,astropy/astropy,MSeifert04/astropy,StuartLittlefair/astropy,mhvk/astropy,lpsinger/astropy,MSeifert04/astropy,stargaser/astropy,lpsinger/astropy,astropy/astropy,saimn/astropy,saimn/astropy,larrybradley/astropy,mhvk/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,stargaser/astropy