Fix missing space in error message.
Fix missing space in error message.

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