ReconsumeLater cause panic

#### Expected behavior

should be `ReconsumeLater`

#### Actual behavior

Panic when call ReconsumeLater

With version 0.6.0
https://github.com/apache/pulsar-client-go/blob/fe3b7c4e445b3de42974ca692574229ad9099a45/pulsar/consumer_impl.go?_pjax=%23js-repo-pjax-container%2C%20div%5Bitemtype%3D%22http%3A%2F%2Fschema.org%2FSoftwareSourceCode%22%5D%20main%2C%20%5Bdata-pjax-container%5D#L481

same panic for 0.7
```
github.com/apache/pulsar-client-go@v0.7.0-candidate-1.0.20211108044248-fe3b7c4e445b/pulsar/consumer_impl.go:481 +0x6ca
```

#### Steps to reproduce

```
client, err := pulsar.NewClient(pulsar.ClientOptions{
URL: addr,
})
if err != nil {
panic(err)
}

consumer, err := client.Subscribe(pulsar.ConsumerOptions{
Topic: "test",
SubscriptionName: "xyz",
})
if err != nil {
panic(err)
}

for {
select {
case cm := <-consumer.Chan():
fmt.Println(string(cm.Payload()))
cm.ReconsumeLater(cm.Message,time.Second)
}
}
```

#### System configuration
**Pulsar version**: 0.6.0

Start with pulsar/consumer_impl.go around line 481 and reproduce the panic using the provided Subscribe and ReconsumeLater example against Pulsar 0.6.0 or the referenced 0.7 build. Trace the ReconsumeLater call from the consumer message path; done means the example returns or schedules ReconsumeLater without panicking.

Written by the indexing model from the issue text.