Added fallback for cases when base value is not set for nontranslatab…

…le fields in ContentUpdateMapper (#73)

src/lib/Data/Mapper/ContentUpdateMapper.php

@@ -45,7 +45,7 @@ public function mapToFormData(ValueObject $contentDraft, array $params = [])
             $data->addFieldData(new FieldData([
                 'fieldDefinition' => $fieldDef,
                 'field' => $field,
-                'value' => $isNonTranslatable
+                'value' => $isNonTranslatable && isset($mappedCurrentFields[$fieldDef->identifier])
                     ? $mappedCurrentFields[$fieldDef->identifier]->value
                     : $field->value,
             ]));