Fix $city always not work

Author: cotox

superbench.sh

@@ -379,7 +379,7 @@ ip_info4() {
 	org=$(python tools.py geoip org)
 	countryCode=$(python tools.py ipip country_code)
 	region=$(python tools.py ipip province)
-	if [ !city ]; then
+	if [ -z $city ]; then
 		city=${region}
 	fi