prestashop exception

[Susanb]

Can anyone tell me what this means please. 

[PrestaShopException]
Property FeatureValue->value is not valid
at line 954 in file classes/ObjectModel.php

949.                 }
950. 
951.                 $message = $this->validateField($field, $value, $id_lang);
952.                 if ($message !== true) {
953.                     if ($die) {
954.                         throw new PrestaShopException($message);
955.                     }
956.                     return $error_return ? $message : false;
957.                 }
958.             }
959.         }
ObjectModelCore->validateFieldsLang - [line 295 - classes/ObjectModel.php]
ObjectModelCore->getFieldsLang - [line 511 - classes/ObjectModel.php]
ObjectModelCore->add - [line 178 - classes/FeatureValue.php] - [2 Arguments]
FeatureValueCore->add - [line 171 - classes/FeatureValue.php]
FeatureValueCore::addFeatureValueImport - [line 1868 - controllers/admin/AdminImportController.php] - [5 Arguments]
AdminImportControllerCore->productImport - [line 3497 - controllers/admin/AdminImportController.php]
AdminImportControllerCore->postProcess - [line 178 - classes/controller/Controller.php]
ControllerCore->run - [line 367 - classes/Dispatcher.php]
DispatcherCore->dispatch - [line 58 - admin/index.php]

[bellini13]

You are adding a new feature whose value is not valid...

Perhaps you can provide some details about what you were trying to do