You have to modify mak.copyFrom, to specify the new bit depth for selection mask.
Modify this code:
mask.copyFrom(ievUINT1, 1, ImageEnView1.SelectionMask.Rowlen, ImageEnView1.SelectionMask.ScanLine[ImageEnView1.SelectionMask.Height-1]);
...to...
mask.copyFrom(ievUINT8, 1, ImageEnView1.SelectionMask.Rowlen, ImageEnView1.SelectionMask.ScanLine[ImageEnView1.SelectionMask.Height-1]);
No problems here replacing TImageEnView with TImageEnVect.