[Bug]: simapp v1 snapshots restore return error with `unordered_txs` extension

[hieuvubk]

When testing system-test, I got an error when run snapshots restore with simapp v1.

extension unordered_txs don't exhausted payload stream

Wonder why we have diff conditions with same snapshot item:

payload := nextItem.GetExtensionPayload()
if payload == nil {
	return nil, io.EOF
}

and

if nextItem.GetExtensionPayload() != nil {
	return fmt.Errorf("extension %s don't exhausted payload stream", metadata.Name)
}

currently failed because 2nd conditon.