Array to string conversion Error

I get the following error
A PHP Error was encountered
Severity: Notice
Message: Array to string conversion
Filename: database/DB_query_builder.php
Line Number: 676
Backtrace:
File: C:\wamp\www\stockfeb2017\app\models\Products_model.php
Line: 66
Function: where
File: C:\wamp\www\stockfeb2017\app\controllers\Products.php
Line: 635
Function: getProductOptionsWithWH


How can I sort this?

Many Thanks