Special case when there are no tox users on the network

src/freedombone-image-customise

     cat <<EOF > $rootdir/usr/bin/list-tox-users
 #!/bin/bash
 users_list=\$(lstox | awk -F ' ' '{\$1=""; print \$0}' | sed -e 's/^[[:space:]]*//' | sort -d)
-no_of_users=\$(echo "\$users_list" | wc -l)
+if [ ! \$users_list ]; then
+    no_of_users=0
+else
+    no_of_users=\$(echo "\$users_list" | wc -l)
+fi
 if [ \$no_of_users -gt 0 ]; then
     echo "\$users_list" > /home/$MY_USERNAME/Users.txt
     chown $MY_USERNAME:$MY_USERNAME /home/$MY_USERNAME/Users.txt