When clicking backup/restore I get the following Critical Error

SQL Error: BIGINT UNSIGNED value is out of range in '((`information_schema`.`TABLES`.`DATA_LENGTH` + `information_schema`.`TABLES`.`INDEX_LENGTH`) - `information_schema`.`TABLES`.`DATA_FREE`)'
Error No: 1690
SQL: SELECT TABLE_NAME AS 'table_name',
table_rows AS 'num_rows', (data_length + index_length - data_free) AS 'size'
FROM information_schema.TABLES
WHERE information_schema.TABLES.table_schema = 'db2144'
AND TABLE_NAME IN ('abc_addresses','abc_ant_messages','abc_banner_descriptions','abc_banner_stat','abc_banners','abc_block_descriptions','abc_block_layouts','abc_block_templates','abc_blocks','abc_categories','abc_categories_to_stores','abc_category_descriptions','abc_collection_descriptions','abc_collections','abc_content_descriptions','abc_contents','abc_contents_to_stores','abc_countries','abc_country_descriptions','abc_coupon_descriptions','abc_coupons','abc_coupons_categories','abc_coupons_products','abc_currencies','abc_custom_blocks','abc_custom_lists','abc_customer_groups','abc_customer_notifications','abc_customer_transactions','abc_customers','abc_dataset_column_properties','abc_dataset_definition','abc_dataset_properties','abc_dataset_values','abc_datasets','abc_download_attribute_values','abc_download_descriptions','abc_downloads','abc_email_templates','abc_encryption_keys','abc_extension_dependencies','abc_extensions','abc_field_descriptions','abc_field_values','abc_fields','abc_fields_group_descriptions','abc_fields_groups','abc_form_descriptions','abc_form_groups','abc_forms','abc_global_attributes','abc_global_attributes_descriptions','abc_global_attributes_groups','abc_global_attributes_groups_descriptions','abc_global_attributes_type_descriptions','abc_global_attributes_types','abc_global_attributes_value_descriptions','abc_global_attributes_values','abc_language_definitions','abc_languages','abc_layouts','abc_length_class_descriptions','abc_length_classes','abc_locations','abc_manufacturers','abc_manufacturers_to_stores','abc_messages','abc_online_customers','abc_order_data','abc_order_data_types','abc_order_downloads','abc_order_downloads_history','abc_order_history','abc_order_options','abc_order_product_stock_locations','abc_order_products','abc_order_status_ids','abc_order_statuses','abc_order_totals','abc_orders','abc_page_descriptions','abc_pages','abc_pages_forms','abc_pages_layouts','abc_product_descriptions','abc_product_discounts','abc_product_filter_descriptions','abc_product_filter_ranges','abc_product_filter_ranges_descriptions','abc_product_filters','abc_product_option_descriptions','abc_product_option_value_descriptions','abc_product_option_values','abc_product_options','abc_product_specials','abc_product_stock_locations','abc_product_tags','abc_products','abc_products_featured','abc_products_related','abc_products_to_categories','abc_products_to_downloads','abc_products_to_stores','abc_resource_descriptions','abc_resource_library','abc_resource_map','abc_resource_types','abc_reviews','abc_settings','abc_stock_statuses','abc_store_descriptions','abc_stores','abc_task_details','abc_task_steps','abc_tasks','abc_tax_class_descriptions','abc_tax_classes','abc_tax_rate_descriptions','abc_tax_rates','abc_url_aliases','abc_user_groups','abc_user_notifications','abc_users','abc_weight_class_descriptions','abc_weight_classes','abc_zone_descriptions','abc_zones','abc_zones_to_locations')
PHP call stack:
#0 /homepages/10/d452417/htdocs/mgbregalia/core/lib/db.php:102
#1 /homepages/10/d452417/htdocs/mgbregalia/core/engine/extensions.php:1162
#2 /homepages/10/d452417/htdocs/mgbregalia/core/engine/extensions.php:383
#3 /homepages/10/d452417/htdocs/mgbregalia/core/lib/db.php:68
#4 /homepages/10/d452417/htdocs/mgbregalia/admin/model/tool/backup.php:390
#5 /homepages/10/d452417/htdocs/mgbregalia/admin/controller/pages/tool/backup.php:149
#6 /homepages/10/d452417/htdocs/mgbregalia/core/engine/dispatcher.php:306
#7 /homepages/10/d452417/htdocs/mgbregalia/core/engine/dispatcher.php:341
#8 /homepages/10/d452417/htdocs/mgbregalia/core/engine/page.php:108
#9 /homepages/10/d452417/htdocs/mgbregalia/core/engine/router.php:205
#10 /homepages/10/d452417/htdocs/mgbregalia/core/engine/router.php:86
#11 /homepages/10/d42417/htdocs/mgbregalia/index.php:97
in /homepages/10/d452417/htdocs/mgbregalia/core/database/amysqli.php on line 137

Hi,
is there a way of removing unavailable downloads from a customer?

I have removed or changed the file - new one shows in customer account but so does the old one and shows as unavailable.

I would like to remove this. I can see the same file in the admin of the customer
    
download/18/7e/0.pdf       
   
   
Missing File

any Ideas how I can achieve this.

Thanks in advance
Paul