I'm having a problem with my app, I'm attempting to save stuff in core data by copying a label, but its giving me this error 

> 
> Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[\_\_NSCFString appendString:]: nil argument'
> 
> 
> 

This is the code 

```
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }

    ClientDownload *currentClientDownload = [[xmlClientDownloadParser clientArray] objectAtIndex:indexPath.row];

    CGRect contentFrame = CGRectMake(45, 2, 265, 30);
    clientName = [[[UILabel alloc] initWithFrame:contentFrame] autorelease];
    clientName.numberOfLines = 2;
    clientName.font = [UIFont boldSystemFontOfSize:12];
    clientName.text = [currentClientDownload NAME];
    [cell.contentView addSubview:clientName];

    CGRect detailFrame1 = CGRectMake(45, 40, 265, 30);
    clientMobile = [[[UILabel alloc] initWithFrame:detailFrame1] autorelease];

    CGRect detailFrame2 = CGRectMake(45, 40, 265, 30);
    clientAccount = [[[UILabel alloc] initWithFrame:detailFrame2] autorelease];

    clientAccount.font = [UIFont systemFontOfSize:10];
    clientAccount.text = [currentClientDownload ACCOUNT];
    clientMobile.font = [UIFont systemFontOfSize:10];
    clientMobile.text = [currentClientDownload MOBILE];

    [cell.contentView addSubview:clientAccount];
    [cell.contentView addSubview:clientMobile];

    NSLog(@"SaveData");
    Clients *client = (Clients *)[NSEntityDescription insertNewObjectForEntityForName:@"Clients" inManagedObjectContext:managedObjectContext];
    if( (clientName.text) || (clientAccount.text) || (clientMobile.text) != NULL)
    {   
        client.ACCOUNT = clientAccount.text;
        client.NAME = clientName.text;
        client.MOBILE = clientMobile.text;
        NSLog(@"CLIENT GENERATED");
        NSError *error;

        if (![managedObjectContext save:&error])
        {
            NSLog(@"Problem saving: %@", [error localizedDescription]);
        }

 }
    NSError * error;
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Clients" inManagedObjectContext:managedObjectContext];
    [fetchRequest setEntity:entity];
    NSArray *fetchedObjects = [managedObjectContext executeFetchRequest:fetchRequest error:&error];

    for (NSManagedObject *info in fetchedObjects)

    {

        NSLog(@"ACCOUNT: %@",[info valueForKey:@"ACCOUNT"]);
        NSLog(@"NAME: %@",[info valueForKey:@"NAME"]);
        NSLog(@"MOBILE: %@",[info valueForKey:@"MOBILE"]);

    }   

    [fetchRequest release];
    return cell; 

}

```