[fix][ml] Cursor ignores the position that has an empty ack-set if disabled deletionAtBatchIndexLevelEnabled (apache#24406)

(cherry picked from commit 3bd70fd)

Author: poorbarcode

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedCursorImpl.java

@@ -2377,7 +2377,7 @@ public void asyncDelete(Iterable<Position> positions, AsyncCallbacks.DeleteCallb
                     }
                     continue;
                 }
-                if (position.ackSet == null) {
+                if (position.ackSet == null || position.ackSet.length == 0) {
                     if (batchDeletedIndexes != null) {
                         batchDeletedIndexes.remove(position);
                     }

managed-ledger/src/test/java/org/apache/bookkeeper/mledger/impl/ManagedCursorTest.java

@@ -5218,5 +5218,20 @@ public void findEntryFailed(ManagedLedgerException exception, Optional<Position>
         assertEquals(positionRef4.get(), position4);
     }
 
+    @Test
+    public void testDeleteBatchedMessageWithEmptyAckSet() throws Exception {
+        ManagedLedgerConfig managedLedgerConfig = new ManagedLedgerConfig();
+        managedLedgerConfig.setDeletionAtBatchIndexLevelEnabled(false);
+        ManagedLedgerImpl ml = (ManagedLedgerImpl) factory.open("testDeleteBatchedMessageWithEmptyAckSet",
+            managedLedgerConfig);
+        ManagedCursorImpl cursor = (ManagedCursorImpl) ml.openCursor("c1");
+        Position position = ml.addEntry(new byte[1]);
+        Position positionWithEmptyAckSet =
+                new PositionImpl(position.getLedgerId(), position.getEntryId(), new long[]{});
+        cursor.delete(positionWithEmptyAckSet);
+        assertEquals(cursor.markDeletePosition, position);
+        ml.delete();
+    }
+
     private static final Logger log = LoggerFactory.getLogger(ManagedCursorTest.class);
 }