rbdeal panics on call to `Close`

[masih]

panic: close of closed channel

goroutine 649 [running]:
github.com/lotus-web3/ribs/rbstor.(*rbs).groupWorker(0xc0006fc000, 0x6)
        /Users/masih/go/pkg/mod/github.com/lotus-web3/ribs@v0.0.0-20230717152524-50fead08f629/rbstor/group_worker.go:18 +0x11b
created by github.com/lotus-web3/ribs/rbstor.(*rbs).Start
        /Users/masih/go/pkg/mod/github.com/lotus-web3/ribs@v0.0.0-20230717152524-50fead08f629/rbstor/rbs.go:82 +0x30
exit status 2