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

DIAGNOSIS:
I0304 05:54:17.469111   24713 main.go:305] ***************************
I0304 05:54:17.469294   24713 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]
I0304 05:54:17.469482   24713 main.go:307] Version release-20200219.0-72-gce4d1e45bb88
I0304 05:54:17.469571   24713 main.go:308] PID: 24713
I0304 05:54:17.469710   24713 main.go:309] UID: 0, GID: 0
I0304 05:54:17.469839   24713 main.go:310] Configuration:
I0304 05:54:17.469945   24713 main.go:311] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0304 05:54:17.470036   24713 main.go:312] 		Platform: ptrace
I0304 05:54:17.470138   24713 main.go:313] 		FileAccess: shared, overlay: false
I0304 05:54:17.470256   24713 main.go:314] 		Network: sandbox, logging: false
I0304 05:54:17.470350   24713 main.go:315] 		Strace: false, max size: 1024, syscalls: []
I0304 05:54:17.470449   24713 main.go:316] ***************************
W0304 05:54:17.470566   24713 main.go:321] Block the TERM signal. This is only safe in tests!
D0304 05:54:17.471253   24713 container.go:159] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0304 05:54:17.480751   24713 container.go:592] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-2": signal 0
D0304 05:54:17.481005   24713 sandbox.go:806] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0304 05:54:17.481227   24713 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0304 05:54:17.481802   24713 urpc.go:534] urpc: successfully marshalled 117 bytes.
I0304 05:54:17.913555   24713 debug.go:122] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2", PID: 12260
I0304 05:54:17.913710   24713 debug.go:131] Retrieving sandbox stacks
D0304 05:54:17.913840   24713 sandbox.go:924] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0304 05:54:17.913986   24713 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
W0304 05:54:17.914208   24713 error.go:48] FATAL ERROR: retrieving stacks: connecting to control server at PID 12260: connection refused
retrieving stacks: connecting to control server at PID 12260: connection refused
W0304 05:54:17.914565   24713 main.go:338] Failure to execute command, err: 1