Fix a crash in feedback list view with attachments

The crash was happening when an attachment was still loading in the last cell but before loading ended, the number of cells changed by deleting a message. Once the attachment was loaded, the crash occured.

This is no fixed by using a safer approach on updating the cell content for loaded attachments by using notifications and letting the cells decide themselves if they need to re-display their content.

Classes/BITFeedbackListViewCell.m

@@ -26,11 +26,13 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#import "HockeySDK.h"
 #import "HockeySDKPrivate.h"
 
 #import "BITFeedbackListViewCell.h"
 #import "BITFeedbackMessageAttachment.h"
 #import "BITActivityIndicatorButton.h"
+#import "BITFeedbackManagerPrivate.h"
 
 #define BACKGROUNDCOLOR_DEFAULT BIT_RGBCOLOR(245, 245, 245)
 #define BACKGROUNDCOLOR_ALTERNATE BIT_RGBCOLOR(235, 235, 235)
@@ -70,6 +72,8 @@
 
 @property (nonatomic, strong) UIView *accessoryBackgroundView;
 
+@property (nonatomic, strong) id updateAttachmentNotification;
+
 @end
 
 
@@ -107,13 +111,53 @@
     _labelText.dataDetectorTypes = UIDataDetectorTypeAll;
     
     _attachmentViews = [NSMutableArray new];
+    [self registerObservers];
   }
   return self;
 }
 
+- (void)dealloc {
+  [self unregisterObservers];
+}
+
 
 #pragma mark - Private
 
+- (void) registerObservers {
+  __weak typeof(self) weakSelf = self;
+  if (nil == _updateAttachmentNotification) {
+    _updateAttachmentNotification = [[NSNotificationCenter defaultCenter] addObserverForName:kBITFeedbackUpdateAttachmentThumbnail
+                                                                                    object:nil
+                                                                                     queue:NSOperationQueue.mainQueue
+                                                                                usingBlock:^(NSNotification *note) {
+                                                                                  typeof(self) strongSelf = weakSelf;
+                                                                                  [strongSelf updateAttachmentFromNotification:note];
+                                                                                }];
+  }
+}
+
+- (void) unregisterObservers {
+  if (_updateAttachmentNotification) {
+    [[NSNotificationCenter defaultCenter] removeObserver:_updateAttachmentNotification];
+    _updateAttachmentNotification = nil;
+  }
+}
+
+- (void) updateAttachmentFromNotification:(NSNotification *)note {
+  if (!self.message) return;
+  if (!self.message.attachments) return;
+  if (self.message.attachments.count == 0) return;
+  if (!note.object) return;
+  if (![note.object isKindOfClass:[BITFeedbackMessageAttachment class]]) return;
+  
+  BITFeedbackMessageAttachment *attachment = (BITFeedbackMessageAttachment *)note.object;
+  if (![self.message.attachments containsObject:attachment]) return;
+  
+  // The attachment is part of the message used for this cell, so lets update it.
+  [self setAttachments:self.message.previewableAttachments];
+  [self setNeedsLayout];
+}
+
 - (UIColor *)backgroundColor {
   
   if (self.backgroundStyle == BITFeedbackListViewCellBackgroundStyleNormal) {

Classes/BITFeedbackListViewController.m

@@ -652,7 +652,7 @@
           if (responseData.length) {
             dispatch_async(dispatch_get_main_queue(), ^{
               [attachment replaceData:responseData];
-              [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];
+              [[NSNotificationCenter defaultCenter] postNotificationName:kBITFeedbackUpdateAttachmentThumbnail object:attachment];
               [[BITHockeyManager sharedHockeyManager].feedbackManager saveMessages];
             });
           }

Classes/BITFeedbackManager.m

@@ -53,6 +53,8 @@
 #define kBITFeedbackLastMessageID   @"HockeyFeedbackLastMessageID"
 #define kBITFeedbackAppID           @"HockeyFeedbackAppID"
 
+NSString *const kBITFeedbackUpdateAttachmentThumbnail = @"BITFeedbackUpdateAttachmentThumbnail";
+
 @interface BITFeedbackManager()<UIGestureRecognizerDelegate>
 
 @property (nonatomic, strong) UITapGestureRecognizer *tapRecognizer;

Classes/BITFeedbackManagerPrivate.h

@@ -30,6 +30,8 @@
 
 #if HOCKEYSDK_FEATURE_FEEDBACK
 
+extern NSString *const kBITFeedbackUpdateAttachmentThumbnail;
+
 #import "BITFeedbackMessage.h"
 
 @interface BITFeedbackManager () <UIAlertViewDelegate> {