Fix timeseries to deal with the MaskedColumn now being read.
Fix timeseries to deal with the MaskedColumn now being read.

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