Fix a bug in constructing mixing columns
Fix a bug in constructing mixing columns

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