Application crashing with Exc_Bad_Thread iPhone - ios

Question

I am trying to implement https://developer.apple.com/library/ios/samplecode/LazyTableImages/Introduction/Intro.html
code for collection view.. Everything is working fine. But in cellForRowAtIndex method while re-loading of old cell the application is crashing. Have a look at code:
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:
(NSInteger)section
{
if (self.galleryItemsArray) {
return [self.galleryItemsArray count];
}
else
{
return 0;
}
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
NSUInteger nodeCount = [self.galleryItemsArray count];
static NSString* simpleTableIdentifier = #"SavedMessageCell_ID";
SavedMessagesCell *cell = [cv dequeueReusableCellWithReuseIdentifier:simpleTableIdentifier forIndexPath:indexPath];
if (cell == nil)
{
cell = [[SavedMessagesCell alloc] initWithFrame:CGRectZero];
}
cell.textLabel.text = [NSString stringWithFormat:#"{%ld,%ld}", (long)indexPath.row, (long)indexPath.section];
if(nodeCount>0)
{
GalleryItemDS *item = [self.galleryItemsArray objectAtIndex:indexPath.row];
// Only load cached images; defer new downloads until scrolling ends
if (!item.imageOfItem)
{
if (gallery_collectionView.dragging == NO && gallery_collectionView.decelerating == NO)
{
[self startIconDownload:item forIndexPath:indexPath];
NSLog(#"%#",item.PhotoPath);
}
// if a download is deferred or in progress, return a placeholder image
cell.image.image = [UIImage imageNamed:#"Icon.png"];
}
else
{
NSLog(#"%#",[NSString stringWithFormat:#"{%ld,%ld}", (long)indexPath.row, (long)indexPath.section]);
NSLog(#"%#",item.PhotoPath);
**cell.image.image = item.imageOfItem; // Crashing here**
}
}
return cell;
}
// -------------------------------------------------------------------------------
// startIconDownload:forIndexPath:
// -------------------------------------------------------------------------------
- (void)startIconDownload:(GalleryItemDS *)galleryItem forIndexPath:(NSIndexPath *)indexPath
{
IconDownloader *iconDownloader = [self.imageDownloadsInProgress objectForKey:indexPath];
if (iconDownloader == nil)
{
iconDownloader = [[IconDownloader alloc] init];
iconDownloader.galleryItem = galleryItem;
[iconDownloader setCompletionHandler:^{
SavedMessagesCell *cell = (SavedMessagesCell *)[gallery_collectionView cellForItemAtIndexPath:indexPath];
// Display the newly loaded image
cell.image.image = galleryItem.imageOfItem;
// cell.backgroundColor = [UIColor colorWithPatternImage:galleryItem.imageOfItem];
// Remove the IconDownloader from the in progress list.
// This will result in it being deallocated.
[self.imageDownloadsInProgress removeObjectForKey:indexPath];
}];
[self.imageDownloadsInProgress setObject:iconDownloader forKey:indexPath];
[iconDownloader startDownload];
}
}
- (void)loadImagesForOnscreenRows
{
if ([self.galleryItemsArray count] > 0)
{
NSArray *visiblePaths = [gallery_collectionView indexPathsForVisibleItems];
for (NSIndexPath *indexPath in visiblePaths)
{
GalleryItemDS *appRecord = [self.galleryItemsArray objectAtIndex:indexPath.row];
if (!appRecord.imageOfItem)
// Avoid the app icon download if the app already has an icon
{
[self startIconDownload:appRecord forIndexPath:indexPath];
}
}
}
}
#pragma mark - UIScrollViewDelegate
// -------------------------------------------------------------------------------
// scrollViewDidEndDragging:willDecelerate:
// Load images for all onscreen rows when scrolling is finished.
// -------------------------------------------------------------------------------
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
if (!decelerate)
{
[self loadImagesForOnscreenRows];
}
}
// -------------------------------------------------------------------------------
// scrollViewDidEndDecelerating:
// -------------------------------------------------------------------------------
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
[self loadImagesForOnscreenRows];
}
Please help me in it.