[BUG] Unexpected results of query Apply with Iterate in subtask in Pegasus

[BingqingLyu]

Describe the bug
A clear and concise description of what the bug is.

The following query (on LDBC dataset) output errors:

g.V().hasLabel('forum').as('forum')
 .select('forum').by(out('containerOf').in('1..3', 'replyOf').endV().has('id', 6047318147162))

The error info client gets is:

GremlinServerError: 500: Status{code=UNKNOWN, description=execution_error: system error: kind(IOError), caused 
by:IOError(kind=System(NotConnected)),   occurred at: 
/work/interactive_engine/executor/engine/pegasus/pegasus/src/data_plane/intra_process.rs:43, ;, cause=null}

and internal error info (in pegasus) is:

thread 'reactor 2' panicked at 'iteration of [13] not found;', /root/moran/new/GraphScope/interactive_engine/executor/engine/pegasus/pegasus/src/operator/iteration/switch.rs:271:21

Additional context

As an optional solution, we can modify the query as following, and it runs well.

g.V().hasLabel('forum').as('forum').select('forum').
by(out('containerOf').union(__.in('replyOf'), __.in('replyOf').in('replyOf')).has('id', 6047318147162).as('message'))