guniprop.c: Avoid creating (temporarily) out-of-bounds pointers
This is detected by UBSan on CHERI systems (e.g. Arm Morello) and could result in non-derefenceable pointers when compiled without optimizations.
This is detected by UBSan on CHERI systems (e.g. Arm Morello) and could result in non-derefenceable pointers when compiled without optimizations.