This is the sql statement from the debugger
UPDATE `jos_hikashop_product`
SET `product_name`='........',`product_url`='',`product_meta_description`='',`product_keywords`='',`product_page_title`='',`product_alias`='',`product_canonical`='',`product_code`='Professionel',`product_tax_id`='11',`product_manufacturer_id`='0',`product_layout`='show_tabular',`product_quantity`='-1',`product_min_per_order`='1',`product_max_per_order`='0',`product_sale_start`='',`product_sale_end`='',`product_msrp`='0.0000000',`product_weight`='0.000',`product_weight_unit`='kg',`product_length`='0.000',`product_width`='0.000',`product_dimension_unit`='m',`product_height`='0.000',`product_published`='1',`product_subscription_id`='1',`product_access`='all',`product_group_after_purchase`='',`product_type`='main',`product_description`='<p>dgsdg</p>',`product_modified`='1382264028'
WHERE `product_id`='11'
i think the "`product_quantity`='-1'" fine and i don't get an db error
Update:
I have set the "`product_quantity`='-1' via sql direct in the db table and it the button is back, but after any change on the product in hika shop the "`product_quantity`=" is set to '0' ....
thats my system
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