应用程序崩溃。当我从自定义表格单元格下载视频的第二个索引时

我正在通过下载视频来开发应用程序。当我正在下载第一个索引视频时，它工作正常。但是当我下载除此视频外。它崩溃了。我的错误显示是：

'NSRangeException'，原因：' *-[__ NSArrayM objectAtIndex：]：索引1超出范围[0 .. 0]'“ *

     -(void)clickbtn:(id)sender{

        btnTag =[sender tag];
         NSLog(@"%d",btnTag);

        NSLog(@"tag number is = %ld",(long)[sender tag]);

        NSString *vedioUrl =[[allData objectAtIndex:btnTag]valueForKey:@"video"];
        NSLog(@"%@",vedioUrl);
       NSString *encodeUrl = [vedioUrl stringByAddingPercentEscapesUsingEncoding:
                             NSASCIIStringEncoding];
        NSLog(@"%@",encodeUrl);


          NSURL *url = [NSURL URLWithString:encodeUrl];
        NSLog(@"%@",url);
        self.downloadManager = [[DownloadManager alloc] initWithDelegate:self];
        self.downloadManager.maxConcurrentDownloads = 4;
        [self.downloadManager addDownloadWithFilename:downloadFilename URL:url];



        self.startDate = [NSDate date];
        [self.downloadManager start];

         UIButton *button1 = (UIButton*)sender;
        NSLog(@"%@",button1);
        CGPoint buttonPosition = [sender convertPoint:CGPointZero
                                               toView:self.Table];

        NSIndexPath *clickedIP = [self.Table indexPathForRowAtPoint:buttonPosition];
        NSLog(@"%@",clickedIP);

        DownloadCell *cell = (DownloadCell *) [self.Table cellForRowAtIndexPath:clickedIP];
        NSLog(@"%@",cell);



        Download *download = self.downloadManager.downloads[clickedIP.row];

        NSLog(@"%@",download);

           if (download.isDownloading)

        {

           [self updateProgressViewForIndexPath:clickedIP download:download];
        }
        else

         {
                 cell.progressView.hidden = YES;
        }
    }