Body mass index Swift signal SIGABRT issues - swift

Question

I'm new in programming. I wrote a code for a body mass index app, but I can't find why I have signal SIGABRT issues.
I didn't find my response or find a good tutorial on stackoverflow.
Can you tell me what is wrong with my code please ?
Thanks
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var lblHeight: UITextField!
#IBOutlet weak var lblWeight: UITextField!
#IBOutlet weak var txtFieldResult: UILabel!
var height = 0.00
var weight = 0.00
var result = 0.00
#IBAction func btnCalcul(sender: UIButton) {
height = (lblHeight.text as NSString).doubleValue
weight = (lblWeight.text as NSString).doubleValue
if height > 0.00 {
result = weight/(height*height)
txtFieldResult.text = "\(result)"}
else {txtFieldResult.text = "Eat please"}
}
}
App delegate info
import UIKit
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// Override point for customization after application launch.
return true
}
func applicationWillResignActive(application: UIApplication) {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
func applicationDidEnterBackground(application: UIApplication) {
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
func applicationWillEnterForeground(application: UIApplication) {
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
func applicationDidBecomeActive(application: UIApplication) {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
func applicationWillTerminate(application: UIApplication) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}
}