bench-all: fix

bench-all

@@ -71,7 +71,7 @@ mkdir "$new_dir"
 do_bench_buildroot_build() (
   arch="$default_arch"
   build_id=bench
-  if [ "$1" = baseline ]; then
+  if [ "${1:-}" = baseline ]; then
     baseline=--baseline
     baseline_suffix=-baseline
   else