test fix: getIndexesShouldNotReturnInvertedIndexes()

Author: rashtao

driver/src/test/java/com/arangodb/async/InvertedIndexTest.java

@@ -182,7 +182,7 @@ void getIndexesShouldNotReturnInvertedIndexes() throws ExecutionException, Inter
         ArangoCollectionAsync collection = db.collection(COLLECTION_NAME);
 
         // create persistent index
-        collection.ensurePersistentIndex(Collections.singletonList("foo"), new PersistentIndexOptions().name("persistentIndex"));
+        collection.ensurePersistentIndex(Collections.singletonList("foo"), new PersistentIndexOptions().name("persistentIndex")).get();
 
         // create inverted index
         String analyzerName = "delimiter-" + UUID.randomUUID();