Merge pull request #52 from ibexa/IBX-5515_fix_empty_fieldtypes_resol…

…ving

IBX-5515: Corrected return type for resolveItemFieldValue function

src/lib/Resolver/ItemResolver.php

@@ -123,7 +123,7 @@ public function resolveItem($args): Item
         return $item;
     }
 
-    public function resolveItemFieldValue(Item $item, $fieldDefinitionIdentifier, $args = null): Field
+    public function resolveItemFieldValue(Item $item, $fieldDefinitionIdentifier, $args = null): ?Field
     {
         return Field::fromField($item->getContent()->getField($fieldDefinitionIdentifier, $args['language'] ?? null));
     }