fix: Skip bootstrap_packages validation when not specified in mkarchiso

scpt/mkarchiso

@@ -1335,6 +1335,7 @@ _validate_requirements_buildmode_bootstrap() {
     local bootstrap_pkg_list_from_file=()
 
     # Check if packages for the bootstrap image are specified
+    if [[ -n "${bootstrap_packages}" ]]; then
         if [[ -e "${bootstrap_packages}" ]]; then
             mapfile -t bootstrap_pkg_list_from_file < \
                 <(sed '/^[[:blank:]]*#.*/d;s/#.*//;/^[[:blank:]]*$/d' "${bootstrap_packages}")
@@ -1347,6 +1348,7 @@ _validate_requirements_buildmode_bootstrap() {
             (( validation_error=validation_error+1 ))
             _msg_error "Bootstrap packages file '${bootstrap_packages}' does not exist." 0
         fi
+    fi
 
     _validate_common_requirements_buildmode_all
     if ! command -v bsdtar &>/dev/null; then