MKUserTrackingBarButtonItem crashes on zoom in - ios7

Question

I am using MKUserTrackingBarButtonItem to track user. I am not able to set the zoom when using user tracking bar button. So i tried to zoom in on the screen .
And application crashes after few steps.
I have a coordinate near by and i am trying to use this to keep track of user relative to the coordinates.
Why is app crashing.
Is there a better way to do this? Any help is greatly appreciated.
Here is my code:-
-(void) viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
self.mapView.delegate = self;
_coordinate1.latitude = 29.9431438;
_coordinate1.longitude = -95.5170326;
self.mapView.showsUserLocation = YES; }
-(void) viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
MKCoordinateRegion region = [self regionFromLocations:self.currentLoc];
[self displayPoints];
MKCoordinateRegion adjustRegion = [self.mapView regionThatFits:region];
self.mapView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
[self.mapView setRegion:adjustRegion animated:YES]; }
- (void)viewDidLoad {
[super viewDidLoad];
MKUserTrackingBarButtonItem *locateMeButton = [[MKUserTrackingBarButtonItem alloc] initWithMapView:self.mapView];
NSArray *toolbarItems = [NSArray arrayWithObjects: locateMeButton,
nil];
self.toolBar.items = toolbarItems; }
- (void)viewWillDisappear:(BOOL)animated {
NSLog(#"viewwillDisapear");
[self.mapView setUserTrackingMode:MKUserTrackingModeNone];
[super viewWillDisappear:animated];}
-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation {
// getting current location
self.currentLoc = userLocation.location.coordinate;
NSLog(#"loc- %f %f", self.currentLoc.longitude, self.currentLoc.latitude); }

Answer 1

Solved the problem by removing map view when view Disappear
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
self.mapView.delegate = nil;
[self.mapView removeFromSuperview];
}