Variants for some products not showing in frontend

-- HikaShop version -- : 2.3.2
-- Joomla version -- : 3.2.4
-- PHP version -- : 5.3.1
-- Browser(s) name and version -- : Firefox 31.0
-- Error-message(debug-mod must be tuned on) -- : Notice: Trying to get property of non-object in .....httpdocs\administrator\components\com_hikashop\classes\product.php on line 613

I am building a shop with products and variants, I have some products where the variants show correctly in the front end and others where they don't appear at all, but from the administrator view the variants are all there and appear to be configured exactly the same in both cases.

The only error message I get appears when I click on manage variants in admin....

Notice: Trying to get property of non-object in E:\wamp\www\apj315\httpdocs\administrator\components\com_hikashop\classes\product.php on line 613

the message is repeated over 100 times before the variants are listed, but the variant listing appears to be correct and when I edit each variant the information is all correct.

I am using template over rides for the product display but f I remove the over ride the problem is still there, what I have found is that if I comment out the line ...

if(isset($variant->map)) continue; //do not display variants dynamically generated because not in the database

I think I've now found a clue to the problem, somewhere along the line I seem to have created characteristics which have been associated with products and then deleted, so they no longer appear in the characteristics table, but the 'variant_characteristic_id' is still associated with the 'variant_product_id' in the variants table. Manually deleting these "ghost" characteristic_id's from the database results in all the variants being listed properly.

Ian

Thank you for the reply Nicolas,

the saving process of the product edition has several checks to clean the data between them.