Allow null values to be passed as a valid value

Author: john.brichevans

src/GDS/Mapper/RESTv1.php

@@ -401,6 +401,11 @@ protected function createPropertyValue(array $arr_field_def, $mix_value)
         }
         $obj_property_value->excludeFromIndexes = !$bol_index;
 
+        if (is_null($mix_value)) {
+            $obj_property_value->nullValue = $mix_value;
+            return $obj_property_value;
+        }
+
         switch ($arr_field_def['type']) {
             case Schema::PROPERTY_STRING:
                 $obj_property_value->stringValue = (string)$mix_value;