Compile error: Cannot use isset() on the result of an expression (you can use "null !== expression"

[ana777]

Please HELP

 

I have the following error on a prestashop 1.7 version when I click in the TopMenu navigation. Everything else seams to work OK. 

 

FatalErrorException in 8bcd7270a031099175bfb93bc8750d28a0a5755b.file.category.tpl.php line 308:

Compile Error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)

 

Does someone knows how to fixe it? Its URGENT!!!

[rocky]

From the error message, there is invalid code like isset($size || $color) in themes/classic/templates/catalog/listing/category.tpl or product-list.tpl. Make sure there is no isset() that has an expression inside it instead of a single variable. For example, the previous code should be isset($size) && isset($color). I can't find any such code in the default theme, so I'm assuming you've modified something.