Fix multinv16.fut.
Fix multinv16.fut.

ihc/futhark,diku-dk/futhark,ihc/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark,diku-dk/futhark,ihc/futhark,HIPERFIT/futhark,HIPERFIT/futhark,mrakgr/futhark,mrakgr/futhark,mrakgr/futhark,diku-dk/futhark,CulpaBS/wbBach