PropertyModifier: Replace Null with String

library/Director/PropertyModifier/PropertyModifierReplaceNull.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Icinga\Module\Director\PropertyModifier;
+
+use Icinga\Module\Director\Hook\PropertyModifierHook;
+use Icinga\Module\Director\Web\Form\QuickForm;
+
+class PropertyModifierReplaceNull extends PropertyModifierHook
+{
+
+    public function getName()
+    {
+        return 'Replace null value with String';
+    }
+
+    public static function addSettingsFormFields(QuickForm $form)
+    {
+        $form->addElement('text', 'string', array(
+            'label'       => 'Replacement String',
+            'description' => $form->translate('Your replacement string'),
+            'required'    => true,
+        ));
+    }
+
+    public function transform($value)
+    {
+        if ($value === null) {
+            return $this->getSetting('string');
+        } else {
+	    return $value;
+	}  
+    }
+}

register-hooks.php

@@ -45,6 +45,7 @@
 use Icinga\Module\Director\PropertyModifier\PropertyModifierRejectOrSelect;
 use Icinga\Module\Director\PropertyModifier\PropertyModifierRenameColumn;
 use Icinga\Module\Director\PropertyModifier\PropertyModifierReplace;
+use Icinga\Module\Director\PropertyModifier\PropertyModifierReplaceNull;
 use Icinga\Module\Director\PropertyModifier\PropertyModifierSimpleGroupBy;
 use Icinga\Module\Director\PropertyModifier\PropertyModifierSkipDuplicates;
 use Icinga\Module\Director\PropertyModifier\PropertyModifierSplit;
@@ -118,6 +119,7 @@
         PropertyModifierRejectOrSelect::class,
         PropertyModifierRenameColumn::class,
         PropertyModifierReplace::class,
+        PropertyModifierReplaceNull::class,
         PropertyModifierSimpleGroupBy::class,
         PropertyModifierSkipDuplicates::class,
         PropertyModifierSplit::class,