A fix to segmented reductions.
A fix to segmented reductions.

ihc/futhark,ihc/futhark,diku-dk/futhark,diku-dk/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,HIPERFIT/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark