Fix: correctly check if environment variables are set

usr/sbin/sshutterd

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/bash -e
 
 function log {
 	echo "$(date +'%Y-%m-%d %H:%M:%S') $@"
@@ -10,7 +10,7 @@ if [ -f "/etc/sshutter.conf" ]; then
 fi
 
 # Check if args are given
-if [ "$WHITELIST" -eq "" ] || [ "$PORT" -eq "" ] || [ "$TARGET" -eq "" ]; then
+if [ "$WHITELIST" == "" ] || [ "$PORT" == "" ] || [ "$TARGET" == "" ]; then
 	echo "Error: you need to specify WHITELIST, PORT and TARGET, either in /etc/sshutter.conf or through environment variables." 1>&2
 	exit 1
 fi