title: Prestashop 1.6.1.4 - Root category must be an integer value
body: <p>I'm trying a fresh installation of prestashop 1.6.1.4, first I got <code>SQL error on query All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead​</code> and used the following solution <a href="https://www.prestashop.com/forums/topic/480947-error-presta-on-server-2012-r2-sql-error-on-query-all-parts-of-a-primary-key-must-be-not-null/" rel="nofollow noreferrer">https://www.prestashop.com/forums/topic/480947-error-presta-on-server-2012-r2-sql-error-on-query-all-parts-of-a-primary-key-must-be-not-null/</a></p>
  
  <p>But now, after install, when I go to admin > catalog I get:</p>
  
  <pre><code>[PrestaShopException]
  
  Root category must be an integer value
  at line 212 in file classes/helper/HelperTreeCategories.php
  
  207.     }
  208. 
  209.     public function setRootCategory($value)
  210.     {
  211.         if (!Validate::isInt($value)) {
  212.             throw new PrestaShopException('Root category must be an integer value');
  213.         }
  214. 
  215.         $this-&gt;_root_category = $value;
  216.         return $this;
  217.     }
  HelperTreeCategoriesCore-&gt;setRootCategory - [line 2504 - controllers/admin/AdminProductsController.php] - [1 Arguments]
  AdminProductsControllerCore-&gt;initContent - [line 189 - classes/controller/Controller.php]
  ControllerCore-&gt;run - [line 367 - classes/Dispatcher.php]
  DispatcherCore-&gt;dispatch - [line 58 - admin1/index.php]
  </code></pre>
  
  <p>$value is empty</p>
  
  <p><strong>Note:</strong> I'm trying to install this specific version because I'm debugging:</p>
  
  <p><a href="https://stackoverflow.com/questions/40847143/cannot-save-or-edit-product-data-in-prestashop-1-6-1-4?noredirect=1#comment68911531_40847143">Cannot save or edit product data in Prestashop 1.6.1.4</a></p>