Initialize attributes with empty values.

Fixes cases in which you create an item and the alias or combined values attribute does not get notified due `isAttributeSet()` returning false.

Author: richardhj

src/MetaModels/DcGeneral/Data/Driver.php

@@ -18,6 +18,7 @@
  * @author     David Molineus <david.molineus@netzmacht.de>
  * @author     binron <rtb@gmx.ch>
  * @author     Sven Baumann <baumann.sv@gmail.com>
+ * @author     Richard Henkenjohann <richardhenkenjohann@googlemail.com>
  * @copyright  2012-2018 The MetaModels team.
  * @license    https://github.com/MetaModels/core/blob/master/LICENSE LGPL-3.0-or-later
  * @filesource
@@ -304,7 +305,7 @@ public function getEmptyConfig()
      */
     public function getEmptyModel()
     {
-        $objItem = new Item($this->getMetaModel(), array());
+        $objItem = new Item($this->getMetaModel(), null);
         return new Model($objItem);
     }
 

src/MetaModels/Item.php

@@ -61,10 +61,19 @@ class Item implements IItem
      *
      * @param IMetaModel $objMetaModel The model this item is represented by.
      *
-     * @param array      $arrData      The initial data that shall be injected into the new instance.
+     * @param array|null $arrData      The initial data that shall be injected into the new instance.
      */
     public function __construct(IMetaModel $objMetaModel, $arrData)
     {
+        if (null === $arrData) {
+            // Initialize attributes with empty values.
+            $arrData = [];
+
+            foreach ($objMetaModel->getAttributes() as $attribute) {
+                $arrData[$attribute->getColName()] = null;
+            }
+        }
+
         $this->arrData   = $arrData;
         $this->metaModel = $objMetaModel;
     }