Error: json_decode(): Argument #1 ($json) must be of type string, array given
File: .\admin\model\catalog\product.php
Line: 771

Backtrace: 0
File: .\admin\model\catalog\product.php
Line: 771
Function: json_decode

Backtrace: 1
File: .\system\engine\loader.php
Line: 343
Class: Opencart\Admin\Model\Catalog\Product
Function: editVariants

Backtrace: 2
File: .\system\engine\proxy.php
Line: 87
Class: Opencart\System\Engine\Loader
Function: Opencart\System\Engine\{closure}

Backtrace: 3
File: .\admin\controller\catalog\product.php
Line: 1261
Class: Opencart\System\Engine\Proxy
Function: __call

Backtrace: 4
File: .\system\engine\action.php
Line: 96
Class: Opencart\Admin\Controller\Catalog\Product
Function: save

Backtrace: 5
File: .\system\framework.php
Line: 259
Class: Opencart\System\Engine\Action
Function: execute

Backtrace: 6
File: .\admin\index.php
Line: 20
Function: require_once