[MOD-2357] iOS: ti.map module crashes application when closing window

   var MapModule = require('ti.map');
   
   var win = Ti.UI.createWindow({
     backgroundColor: "white",
     title: 'Window 1'
   });
   
   var btn = Ti.UI.createButton({
     title: 'Trigger'
   });
   
   win.add(btn);
   
   var nav = Ti.UI.iOS.createNavigationWindow({
     window: win
   });
   
   btn.addEventListener('click', function() {
     var win2 = Ti.UI.createWindow({
       title: 'Window 2'
     });
     
     var pin1 = MapModule.createAnnotation({  
       latitude: 37.390749,
       longitude: -122.081651,
       title: "Title1 ",
       subtitle: 'Mountain View, CA',
       pincolor: MapModule.ANNOTATION_RED,
     }); 
      
     var mapview = MapModule.createView({  
       region: {
         latitude: 37.390749,
         longitude: -122.081651,
       },
       annotations: [pin1]
     }); 
   
     win2.add(mapview);
     nav.openWindow(win2);
   })
   
   nav.open();