it seems that your scan end with no result did you enable monitor mode as in the first post ? if not : (you can load monitor mode with cleven or manually following this commands )
1-load the drivers
2-type these commands after root
ifconfig wlan0 down
iwconfig wlan0 mode monitor
ifconfig wlan0 up
3- run the script
4-to reset managed mode type after root :
ifconfig wlan0 down
iwconfig wlan0 mode managed
ifconfig wlan0 up
hope this help