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

DIAGNOSIS:
I0305 01:31:17.341343   27127 main.go:305] ***************************
I0305 01:31:17.341545   27127 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]
I0305 01:31:17.341823   27127 main.go:307] Version release-20200219.0-72-gce4d1e45bb88
I0305 01:31:17.341987   27127 main.go:308] PID: 27127
I0305 01:31:17.342103   27127 main.go:309] UID: 0, GID: 0
I0305 01:31:17.342255   27127 main.go:310] Configuration:
I0305 01:31:17.342340   27127 main.go:311] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0305 01:31:17.342470   27127 main.go:312] 		Platform: ptrace
I0305 01:31:17.342554   27127 main.go:313] 		FileAccess: shared, overlay: false
I0305 01:31:17.342736   27127 main.go:314] 		Network: sandbox, logging: false
I0305 01:31:17.342856   27127 main.go:315] 		Strace: false, max size: 1024, syscalls: []
I0305 01:31:17.342953   27127 main.go:316] ***************************
W0305 01:31:17.343100   27127 main.go:321] Block the TERM signal. This is only safe in tests!
D0305 01:31:17.343501   27127 container.go:159] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0305 01:31:17.352364   27127 container.go:592] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-1": signal 0
D0305 01:31:17.352552   27127 sandbox.go:806] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0305 01:31:17.352690   27127 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0305 01:31:17.353245   27127 urpc.go:534] urpc: successfully marshalled 117 bytes.
I0305 01:31:19.260217   27127 debug.go:122] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1", PID: 1027
I0305 01:31:19.260359   27127 debug.go:131] Retrieving sandbox stacks
D0305 01:31:19.260528   27127 sandbox.go:924] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
D0305 01:31:19.260654   27127 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-1"
W0305 01:31:19.260885   27127 error.go:48] FATAL ERROR: retrieving stacks: connecting to control server at PID 1027: connection refused
retrieving stacks: connecting to control server at PID 1027: connection refused
W0305 01:31:19.261286   27127 main.go:338] Failure to execute command, err: 1