Fix: unbound variable _UNBUFFERED ()

update-Nitrov3.sh

@@ -5,7 +5,7 @@ set -euo pipefail
 
 # Real-time output via pseudo-terminal (unbuffer from expect)
 # Dit forceert line-buffered output voor ALLE commands, ook in web interfaces
-if [ -z "$_UNBUFFERED" ] && command -v unbuffer &> /dev/null; then
+if [ -z "${_UNBUFFERED:-}" ] && command -v unbuffer &> /dev/null; then
     export _UNBUFFERED=1
     exec unbuffer bash "$0" "$@"
 fi