An unhandled exception on checking the owner of my class

Question

When I try to check if the Person Email of that Colector is right my program crashes saying that An unhandled exception of type 'System.NullReferenceException' occurred in Aplicativo Windows Phone.dll. Why? The error is happening on the

   if (Coletor.Pessoa.Email == email)
   {
       Coletores.Add(Coletor);
   }

My Coletor class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Linq.Mapping;
using System.Data.Linq;
using Microsoft.Phone.Data.Linq;
using Microsoft.Phone.Data.Linq.Mapping;
using System.ComponentModel;

namespace Aplicativo_Windows_Phone
{
#pragma warning disable 0169, 0649
    [Table(Name = "Coletores")]
    public class Coletor : INotifyPropertyChanged
    {
        private int _id;
        [Column(IsPrimaryKey = true, IsDbGenerated = true)]
        public int Id { get { return _id; }
            set { _id = value;
            OnPropertyChanged("Id");
            }
        }

        private float _lat;
        [Column]
        public float Latitude { get { return _lat; }
            set { _lat = value;
            OnPropertyChanged("Latitude");
            }
        }

        private float _long;
        [Column]
        public float Longitude { get { return _long; }
            set { _long = value;
            OnPropertyChanged("Longitude");
            }
        }

        [Column(Name = "Pessoa")]
        private int? pessoaId;
        private EntityRef<Pessoa> _pessoa = new EntityRef<Pessoa>();
        [Association(Name = "FK_Coletores_ColetorPessoas", IsForeignKey = true, Storage = "_pessoa", ThisKey = "pessoaId")]
        public Pessoa Pessoa
        {
            get { return _pessoa.Entity; }
            set { _pessoa.Entity = value; }
        }


        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string name)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }
    }
}

The code that I am trying to check the person email:

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            if (NavigationContext.QueryString.TryGetValue("email", out email))
            {
                List<HyperlinkButton> listaLinks = new List<HyperlinkButton>();

                AppDataContext db = new AppDataContext();

                List<Coletor> Coletores = new List<Coletor>();

                foreach (var Coletor in db.Coletores)
                {
                    if (Coletor.Pessoa.Email == email)
                    {
                        Coletores.Add(Coletor);
                    }
                }
                int i = 0;
                foreach( Coletor coletor in Coletores)
                {
                    HyperlinkButton aux = new HyperlinkButton();
                    aux.Content = "Coletor " + (i + 1).ToString();
                    aux.FontSize = 24;
                    aux.NavigateUri = new Uri("/OcorrenciasPage.xaml?coletorId=" + coletor.Id.ToString(), UriKind.RelativeOrAbsolute);
                    listaLinks.Add(aux);
                    i++;
                }

                ListBox coletores = new ListBox();
                coletores.ItemsSource = listaLinks;
                stcList.Children.Add(coletores);
            }
            base.OnNavigatedTo(e);
        }

I think the error is in my class, that I did something wrong on the relationship with the other class.

Ps. My Coletor belongs to just one Pessoa, but one Pessoa can have many Coletors.