防止NSArray由於nil對象崩潰

NSArray *titles = @[QHLocalizedString(@"商戶名稱", nil), QHLocalizedString(@"聯繫方式", nil), QHLocalizedString(@"派運之星", nil), QHLocalizedString(@"商戶類型", nil), QHLocalizedString(@"商戶地址", nil), QHLocalizedString(@"詳細地址", nil), QHLocalizedString(@"商戶評價", nil), QHLocalizedString(@"商戶說明", nil)];
NSArray *descs = @[@"merchantName", _supportCurrencyModel.username, @"luckStarNum", @"merType", @"merchantAddress", @"detailedAddress", @"commentstar", @"merDesc", @"merImgList"];
for (int i = 0; i<titles.count; i++) {
    QHChainTitleValueItem *item = [[QHChainTitleValueItem alloc] init];
    item.leftTitle = titles[i];
    if ([titles[i] isEqualToString:QHLocalizedString(@"聯繫方式", nil)]) {
       item.rightTitle = descs[i];
    }else {
       item.rightTitle = [_model valueForKey:descs[i]];
    }
     [_dataArray addObject:item];
}