Panic when trying to pull nonexistent output

[oldsj]

cloudexec pull output panics if the last job failed / had no output to pull:

 cloudexec pull output                                                                                                                 (base) 
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x10516bb0c]

goroutine 1 [running]:
main.main.func8(0x1400013a180)
        /Users/jamesolds/dev/cloudexec/cmd/cloudexec/main.go:318 +0x35c
github.com/urfave/cli/v2.(*Command).Run(0x140001289a0, 0x1400013a180, {0x140001382c0, 0x2, 0x2})
        /Users/jamesolds/go/pkg/mod/github.com/urfave/cli/v2@v2.25.1/command.go:274 +0x730
github.com/urfave/cli/v2.(*Command).Run(0x14000129600, 0x1400013a0c0, {0x140000202a0, 0x3, 0x3})
        /Users/jamesolds/go/pkg/mod/github.com/urfave/cli/v2@v2.25.1/command.go:267 +0x940
github.com/urfave/cli/v2.(*App).RunContext(0x14000124000, {0x1055f1f48?, 0x105a80240}, {0x140000202a0, 0x3, 0x3})
        /Users/jamesolds/go/pkg/mod/github.com/urfave/cli/v2@v2.25.1/app.go:332 +0x518
github.com/urfave/cli/v2.(*App).Run(...)
        /Users/jamesolds/go/pkg/mod/github.com/urfave/cli/v2@v2.25.1/app.go:309
main.main()
        /Users/jamesolds/dev/cloudexec/cmd/cloudexec/main.go:513 +0x17bc