avoid panic

[s1mple1122]

I found that many users panicked when using lotus-miner sealing workers,The reason is that previous versions have checked the value of eBar ,But it's ignored here
Worker 8afb3048-9bf5-4927-a380-f2ec13410f36, host (disabled)
panic: strings: negative Repeat count

goroutine 1 [running]:
strings.Repeat(0x39b3742, 0x1, 0x8000000000000000, 0xc0004ee000, 0xc00109efc0)
	/mnt/build/go/src/strings/strings.go:529 +0x5e5
main.barString(0x0, 0x0, 0x0, 0x15, 0xc00109f2b8)
	/home/fc01/compile-quantum/lotus/cmd/lotus-miner/sealing.go:45 +0x126
main.glob..func56(0xc000354cc0, 0x0, 0x0)
	/home/fc01/compile-quantum/lotus/cmd/lotus-miner/sealing.go:132 +0xdca
github.com/urfave/cli/v2.(*Command).Run(0x54f9780, 0xc000354bc0, 0x0, 0x0)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/command.go:164 +0x4dd
github.com/urfave/cli/v2.(*App).RunAsSubcommand(0xc0003a4d80, 0xc0003549c0, 0x0, 0x0)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/app.go:427 +0xa49
github.com/urfave/cli/v2.(*Command).startApp(0x54f9c00, 0xc0003549c0, 0x7ffdd3d0c666, 0x7)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/command.go:279 +0x6bb
github.com/urfave/cli/v2.(*Command).Run(0x54f9c00, 0xc0003549c0, 0x0, 0x0)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/command.go:94 +0x9cd
github.com/urfave/cli/v2.(*App).RunContext(0xc0003a4c00, 0x3f1c090, 0xc0000528f8, 0xc00004e180, 0x3, 0x3, 0x0, 0x0)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/app.go:306 +0x810
github.com/urfave/cli/v2.(*App).Run(...)
	/home/fc01/go/pkg/mod/github.com/urfave/cli/[email protected]/app.go:215
github.com/filecoin-project/lotus/cli.RunApp(0xc0003a4c00)
	/home/fc01/compile-quantum/lotus/cli/helper.go:35 +0x7c
main.main()
	/home/fc01/compile-quantum/lotus/cmd/lotus-miner/main.go:166 +0xf05

[codecov]

Codecov Report

Merging #8205 (296ae43) into master (6d0066e) will decrease coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #8205      +/-   ##
==========================================
- Coverage   40.29%   40.18%   -0.12%     
==========================================
  Files         666      666              
  Lines       72767    72769       +2     
==========================================
- Hits        29320    29239      -81     
- Misses      38316    38395      +79     
- Partials     5131     5135       +4     

Impacted Files	Coverage Δ
cmd/lotus-miner/sealing.go	42.77% <100.00%> (+0.66%)	⬆️
itests/kit/blockminer.go	70.16% <0.00%> (-19.34%)	⬇️
chain/actors/builtin/miner/diff.go	48.52% <0.00%> (-10.30%)	⬇️
chain/events/observer.go	71.64% <0.00%> (-8.21%)	⬇️
miner/miner.go	54.42% <0.00%> (-4.60%)	⬇️
node/impl/full/mpool.go	46.95% <0.00%> (-1.74%)	⬇️
blockstore/autobatch.go	56.30% <0.00%> (-1.69%)	⬇️
chain/gen/gen.go	68.19% <0.00%> (-1.23%)	⬇️
extern/sector-storage/stores/local.go	59.16% <0.00%> (-0.84%)	⬇️
chain/sync_manager.go	66.77% <0.00%> (-0.63%)	⬇️
... and 13 more

---

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[silvianetobessa]

Hello @s1mple1122 !

This contribution to the Filecoin codebase was voted as impactful during Q1 and is eligible for a FIL prize as part of a Protocol Labs experiment to reward open source contributions from the community (see full details here).

Please reach out to us through [email protected] to receive the instructions on how to claim your reward!