crashfix: crash while accessing image property

assert on blind cast

// FREEBIE

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -2202,10 +2202,17 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
                 if ([[messageItem media] isKindOfClass:[TSPhotoAdapter class]]) {
                     TSPhotoAdapter *messageMedia = (TSPhotoAdapter *)[messageItem media];
 
-                    UIImage *tappedImage = ((UIImageView *)[messageMedia mediaView]).image;
+                    UIView *mediaView = [messageMedia mediaView];
+                    if (![mediaView isKindOfClass:[UIImageView class]]) {
+                        OWSFail(@"unexpected mediaView of type: %@", [mediaView class]);
+                        return;
+                    }
+                    UIImageView *imageView = (UIImageView *)mediaView;
+                    UIImage *tappedImage = imageView.image;
                     if (tappedImage == nil) {
                         DDLogWarn(@"tapped TSPhotoAdapter with nil image");
-                    } else {
+                        return;
+                    }
                     UIWindow *window = [UIApplication sharedApplication].keyWindow;
                     JSQMessagesCollectionViewCell *cell
                         = (JSQMessagesCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
@@ -2214,14 +2221,13 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 
                     __block TSAttachment *attachment = nil;
                     [self.uiDatabaseConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
-                            attachment = [TSAttachment fetchObjectWithUniqueID:messageMedia.attachmentId
-                                                                   transaction:transaction];
+                        attachment =
+                            [TSAttachment fetchObjectWithUniqueID:messageMedia.attachmentId transaction:transaction];
                     }];
 
                     if ([attachment isKindOfClass:[TSAttachmentStream class]]) {
                         TSAttachmentStream *attStream = (TSAttachmentStream *)attachment;
-                            FullImageViewController *vc =
-                                [[FullImageViewController alloc] initWithAttachment:attStream
+                        FullImageViewController *vc = [[FullImageViewController alloc] initWithAttachment:attStream
                                                                                                  fromRect:convertedRect
                                                                                            forInteraction:interaction
                                                                                               messageItem:messageItem
@@ -2229,7 +2235,6 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 
                         [vc presentFromViewController:self];
                     }
-                    }
                 } else if ([[messageItem media] isKindOfClass:[TSAnimatedAdapter class]]) {
                     // Show animated image full-screen
                     TSAnimatedAdapter *messageMedia = (TSAnimatedAdapter *)[messageItem media];