Fixed bug in CopyCtPropFold.hs, causing the following program to throw a typeError.
Fixed bug in CopyCtPropFold.hs, causing the following program to throw a typeError.

fun int main(int a) =
  a pow 0

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