Use fallback when data type is missing

Uses the existing getForExtract() logic to get a fallback data type.
Fixes #1439

application/src/Api/Adapter/AbstractResourceEntityAdapter.php

@@ -478,7 +478,7 @@ public function getFulltextText($resource)
  $texts = [];
  foreach ($resource->getValues()->matching($criteria) as $value) {
  $valueRepresentation = new ValueRepresentation($value, $services);
- $texts[] = $dataTypes->get($value->getType())->getFulltextText($view, $valueRepresentation);
+ $texts[] = $dataTypes->getForExtract($value)->getFulltextText($view, $valueRepresentation);
  }
  return implode("\n", $texts);
  }