Wild Horses JavaScript cannot read horse

I’m not sure what I’m doing wrong, but with my code it keeps saying “TypeError: Cannot read property ‘x’ of undefined.” Can I get some help here?
while(true) {
// How do you find the nearest friendly unit?
var horse = hero.findFriends();

if (horse) {
    var x1 = horse.pos.x - 7;
    var x2 = horse.pos.x + 7;
    if (x1 >= 1) {
        // Move to the horse's y position but use x1 for the x position.
        hero.moveXY(x1, horse.pos.y);
    } else if (x2 <= 79) {
        // Move to the horse's y position but use x2 for the x position.
        hero.moveXY(x2, horse.pos.y);
    }
    var distance = hero.distanceTo(horse);
    if (distance <= 10) {
        hero.say("Whoa");
        // Move to the red x to return the horse to the farm.
        hero.moveXY(28, 54);
        // Move back out into the pasture to begin looking for the next horse.
        hero.moveXY(40, 40);
    }
}

}

var horse = hero.findNearest(hero.findFriends());