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

DIAGNOSIS:
I0303 19:42:24.059116    2559 main.go:305] ***************************
I0303 19:42:24.059307    2559 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]
I0303 19:42:24.059540    2559 main.go:307] Version release-20200219.0-72-gce4d1e45bb88
I0303 19:42:24.059681    2559 main.go:308] PID: 2559
I0303 19:42:24.059850    2559 main.go:309] UID: 0, GID: 0
I0303 19:42:24.059971    2559 main.go:310] Configuration:
I0303 19:42:24.060082    2559 main.go:311] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0303 19:42:24.060194    2559 main.go:312] 		Platform: ptrace
I0303 19:42:24.060296    2559 main.go:313] 		FileAccess: shared, overlay: false
I0303 19:42:24.060417    2559 main.go:314] 		Network: sandbox, logging: false
I0303 19:42:24.060552    2559 main.go:315] 		Strace: false, max size: 1024, syscalls: []
I0303 19:42:24.060681    2559 main.go:316] ***************************
W0303 19:42:24.060789    2559 main.go:321] Block the TERM signal. This is only safe in tests!
D0303 19:42:24.061022    2559 container.go:159] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0303 19:42:24.068797    2559 container.go:592] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-2": signal 0
D0303 19:42:24.069008    2559 sandbox.go:806] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0303 19:42:24.069193    2559 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0303 19:42:24.069804    2559 urpc.go:534] urpc: successfully marshalled 117 bytes.
I0303 19:42:24.534272    2559 debug.go:122] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2", PID: 63852
I0303 19:42:24.534420    2559 debug.go:131] Retrieving sandbox stacks
D0303 19:42:24.536172    2559 sandbox.go:924] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
D0303 19:42:24.536271    2559 sandbox.go:318] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-2"
W0303 19:42:24.536453    2559 error.go:48] FATAL ERROR: retrieving stacks: connecting to control server at PID 63852: connection refused
retrieving stacks: connecting to control server at PID 63852: connection refused
W0303 19:42:24.536875    2559 main.go:338] Failure to execute command, err: 1