panic: runtime error: index out of range [1] with length 0

DIAGNOSIS:
I0304 19:10:17.119537   34101 main.go:305] ***************************
I0304 19:10:17.119718   34101 main.go:306] Args: [/syzkaller/managers/ptrace-proxy-sandbox-race/current/image -root /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root -watchdog-action=panic -network=none -debug -alsologtostderr -platform=ptrace -file-access=shared -network=sandbox -TESTONLY-unsafe-nonroot debug -stacks --ps ci-gvisor-ptrace-proxy-sandbox-race-1]
I0304 19:10:17.119935   34101 main.go:307] Version release-20200219.0-72-gce4d1e45bb88
I0304 19:10:17.120061   34101 main.go:308] PID: 34101
I0304 19:10:17.120160   34101 main.go:309] UID: 0, GID: 0
I0304 19:10:17.120253   34101 main.go:310] Configuration:
I0304 19:10:17.120336   34101 main.go:311] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0304 19:10:17.120438   34101 main.go:312] 		Platform: ptrace
I0304 19:10:17.120509   34101 main.go:313] 		FileAccess: shared, overlay: false
I0304 19:10:17.120599   34101 main.go:314] 		Network: sandbox, logging: false
I0304 19:10:17.120691   34101 main.go:315] 		Strace: false, max size: 1024, syscalls: []
I0304 19:10:17.120752   34101 main.go:316] ***************************
W0304 19:10:17.120825   34101 main.go:321] Block the TERM signal. This is only safe in tests!
D0304 19:10:17.121036   34101 container.go:159] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0304 19:10:17.129937   34101 container.go:592] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-1": signal 0
D0304 19:10:17.130126   34101 sandbox.go:806] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0304 19:10:17.130268   34101 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0304 19:10:17.130927   34101 urpc.go:534] urpc: successfully marshalled 117 bytes.
I0304 19:10:17.628613   34101 debug.go:122] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1", PID: 30744
I0304 19:10:17.628735   34101 debug.go:131] Retrieving sandbox stacks
D0304 19:10:17.628849   34101 sandbox.go:924] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0304 19:10:17.628956   34101 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
W0304 19:10:17.629151   34101 error.go:48] FATAL ERROR: retrieving stacks: connecting to control server at PID 30744: connection refused
retrieving stacks: connecting to control server at PID 30744: connection refused
W0304 19:10:17.629589   34101 main.go:338] Failure to execute command, err: 1