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

goroutine 749082 [running]:
DIAGNOSIS:
I0305 07:41:27.899635   27844 main.go:305] ***************************
I0305 07:41:27.899778   27844 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-2]
I0305 07:41:27.900014   27844 main.go:307] Version release-20200219.0-72-gce4d1e45bb88
I0305 07:41:27.900131   27844 main.go:308] PID: 27844
I0305 07:41:27.900223   27844 main.go:309] UID: 0, GID: 0
I0305 07:41:27.900350   27844 main.go:310] Configuration:
I0305 07:41:27.900409   27844 main.go:311] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0305 07:41:27.900470   27844 main.go:312] 		Platform: ptrace
I0305 07:41:27.900542   27844 main.go:313] 		FileAccess: shared, overlay: false
I0305 07:41:27.900637   27844 main.go:314] 		Network: sandbox, logging: false
I0305 07:41:27.900699   27844 main.go:315] 		Strace: false, max size: 1024, syscalls: []
I0305 07:41:27.900799   27844 main.go:316] ***************************
W0305 07:41:27.900866   27844 main.go:321] Block the TERM signal. This is only safe in tests!
D0305 07:41:27.901009   27844 container.go:159] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0305 07:41:27.907285   27844 container.go:592] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-2": signal 0
D0305 07:41:27.907452   27844 sandbox.go:806] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0305 07:41:27.907559   27844 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0305 07:41:27.908091   27844 urpc.go:534] urpc: successfully marshalled 117 bytes.
I0305 07:41:28.610918   27844 debug.go:122] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2", PID: 20431
I0305 07:41:28.611101   27844 debug.go:131] Retrieving sandbox stacks
D0305 07:41:28.611202   27844 sandbox.go:924] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0305 07:41:28.611313   27844 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
W0305 07:41:28.611523   27844 error.go:48] FATAL ERROR: retrieving stacks: connecting to control server at PID 20431: connection refused
retrieving stacks: connecting to control server at PID 20431: connection refused
W0305 07:41:28.611901   27844 main.go:338] Failure to execute command, err: 1