Possible crash of a modal window call ?

I still see some random crash my app and I would like your opinion on it because I wonder if that's not a problem.

To display a modal window, I do this (see code below). Why, because I have to display a webview and if I do not do this, the web page is not displayed in the webview. inside this window, I appeal to other modal windows that are called either in this way, either as standard. Do you think it can be a problem and it can be a cause of the crash?

var = new vueOrdonnance OrdonnanceWindowController (null, vuePrestation);

vueOrdonnance.Window.Title = NSBundle.MainBundle.LocalizedString("Ordonnance","Ordonnance",GlobalClass.strLangueUtilisateur.ToLower() + ".lproj / Localizable");

vueOrdonnance.Window.Center ();
vueOrdonnance.Window.Level = NSWindowLevel.Floating;

IntPtr modalSession;

modalSession = NSApplication.SharedApplication.BeginModalSession (vueOrdonnance.Window);

while (vueOrdonnance.Running)
{
NSApplication.SharedApplication.RunModalSession (modalSession);
NSRunLoop.Current.RunUntil (NSRunLoopMode.Default, NSDate.DistantFuture);
}

vueOrdonnance.Close ();

NSApplication.SharedApplication.EndModalSession (modalSession);