Merge pull request omeka#1489 from Daniel-KM/feature/return_value

Returned an array when fetching all values when there is no result.

application/src/Api/Representation/AbstractResourceEntityRepresentation.php

@@ -313,7 +313,7 @@ public function values()
      * - all: (false) If true, returns all values that match criteria. If false,
      *   returns the first matching value.
      * - default: (null) Default value if no values match criteria. Returns null
-     *   by default.
+     *   by default for single result, empty array for all results.
      * - lang: (null) Get values of this language only. Returns values of all
      *   languages by default.
      * @return ValueRepresentation|ValueRepresentation[]|mixed
@@ -328,7 +328,7 @@ public function value($term, array $options = [])
             $options['all'] = false;
         }
         if (!isset($options['default'])) {
-            $options['default'] = null;
+            $options['default'] = $options['all'] ? [] : null;
         }
         if (!isset($options['lang'])) {
             $options['lang'] = null;