title: Exception [NSNull isEqualToString:]: unrecognized selector when i click on calloutAccessoryControlTapped
body: <p>i have a problem with that exception, actually, when i click on the <code>calloutAccessoryControlTapped</code> button of the pin i got this exception, i try to track the error by the <code>NSLog</code> in the console and i found the only pin which caused this exception have the value <code>&lt;null&gt;</code>, i explain by some code :</p>
  
  <pre><code>for (int i=0; i&lt;[array count]; i++) {
             NSDictionary *stationEnCours=[array objectAtIndex:i];
             location2D = (CLLocationCoordinate2D){ .latitude = lat, .longitude = lng };
             MyLocation *annotation=[[[MyLocation alloc]initWithName:ensStation distanceVersLaStation:distance coordinate:location2D]autorelease];
  
  //here we set the properties before we get call to addAnnotation annotation.stationAdress=[stationEnCours objectForKey:@"ssiphone_adresse"];
             NSLog(@"%@",annotation.stationAdress);
             [mapView addAnnotation:annotation];
  }
  </code></pre>
  
  <p>i have 4 stations, in the console i got this :</p>
  
  <pre><code>2011-05-11 22:27:11.768 TopStation[2370:207] A 51 - Aire de la Champouse
  2011-05-11 22:27:11.769 TopStation[2370:207] &lt;null&gt;
  2011-05-11 22:27:11.769 TopStation[2370:207] 467 Avenue Henri Mauriat
  2011-05-11 22:27:11.769 TopStation[2370:207] Route de Berre - Jas de Bouffan
  </code></pre>
  
  <p>the second one is which cause problem later when i try to click on its <code>calloutAccessoryControlTapped</code> so i checked my database and its adress is a <code>string</code> and it's not <code>null</code>.
  i am little confused, why that exception although all is retrieved as <code>String</code> ?? i have also tried to do the same work but on the server side and all is ok, it's not displaying me <code>NULL</code>, only in the iPhone side and for this station.
  If this help, the adress of the station which make problem is :
  <strong>1 Boulevard du Maréchal Juin</strong></p>