Don't throw exception for unmapped bundles

Closes #3333585

src/SparqlEntityStorageFieldHandler.php

@@ -364,11 +364,7 @@ class SparqlEntityStorageFieldHandler implements SparqlEntityStorageFieldHandler
    */
   public function getInboundBundleValue(string $entity_type_id, string $bundle_uri): array {
     $inbound_map = $this->getInboundMap($entity_type_id);
-    if (empty($inbound_map['bundles'][$bundle_uri])) {
-      throw new \Exception("A bundle mapped to <$bundle_uri> was not found.");
-    }
-
-    return $inbound_map['bundles'][$bundle_uri];
+    return $inbound_map['bundles'][$bundle_uri] ?? [];
   }
 
   /**