Piping yes to stream deletion causes SIGSEGV

[LucasRxTx]

yes yes | nats str delete SOME_STREAM When SOME_STREAM is the name of an actual stream, will SIGSEGV.

? Really delete Stream Junk (y/N) panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x83b0fc9]
goroutine 1 [running]:
github.com/AlecAivazis/survey/v2/terminal.(*RuneReader).ReadLine(0x57303e00, 0x0, 0x8d51968, 0x5700e110, 0x89a3a74, 0x5700e118, 0x57303e00)
    /Users/rip/go/pkg/mod/github.com/!alec!aivazis/survey/v2@v2.2.7/terminal/runereader.go:56 +0x3b9
github.com/AlecAivazis/survey/v2.(*Confirm).getBool(0x57084f00, 0x8874000, 0x570b5364, 0x87c5d00, 0x0, 0x0)
    /Users/rip/go/pkg/mod/github.com/!alec!aivazis/survey/v2@v2.2.7/confirm.go:57 +0x109
github.com/AlecAivazis/survey/v2.(*Confirm).Prompt(0x57084f00, 0x570b5364, 0x5700e108, 0x89a6b58, 0x5700e110, 0x89a3a74)
    /Users/rip/go/pkg/mod/github.com/!alec!aivazis/survey/v2@v2.2.7/confirm.go:136 +0xe5
github.com/AlecAivazis/survey/v2.Ask(0x5727fdf4, 0x1, 0x1, 0x8732240, 0x5701f7f4, 0x0, 0x0, 0x0, 0x5706ca20, 0x811cc0b)
    /Users/rip/go/pkg/mod/github.com/!alec!aivazis/survey/v2@v2.2.7/survey.go:293 +0x400
github.com/AlecAivazis/survey/v2.AskOne(...)
    /Users/rip/go/pkg/mod/github.com/!alec!aivazis/survey/v2@v2.2.7/survey.go:236
main.askConfirmation(0x57026aa0, 0x19, 0x5727fe00, 0x1, 0x1, 0x57026aa0)
    /Users/rip/go/src/github.com/nats-io/natscli/nats/util.go:273 +0xe3
main.(*streamCmd).rmAction(0x57124500, 0x5724e0a0, 0x0, 0x0)
    /Users/rip/go/src/github.com/nats-io/natscli/nats/stream_command.go:1701 +0x174
gopkg.in/alecthomas/kingpin%2ev2.(*actionMixin).applyActions(0x57302e4c, 0x5724e0a0, 0x0, 0x0)
    /Users/rip/go/pkg/mod/gopkg.in/alecthomas/kingpin.v2@v2.2.6/actions.go:28 +0x51
gopkg.in/alecthomas/kingpin%2ev2.(*Application).applyActions(0x57120900, 0x5724e0a0, 0x0, 0x0)
    /Users/rip/go/pkg/mod/gopkg.in/alecthomas/kingpin.v2@v2.2.6/app.go:557 +0xb6
gopkg.in/alecthomas/kingpin%2ev2.(*Application).execute(0x57120900, 0x5724e0a0, 0x57318200, 0x2, 0x2, 0x0, 0x0, 0x0, 0x877a940)
    /Users/rip/go/pkg/mod/gopkg.in/alecthomas/kingpin.v2@v2.2.6/app.go:390 +0x7d
gopkg.in/alecthomas/kingpin%2ev2.(*Application).Parse(0x57120900, 0x57016128, 0x3, 0x3, 0x1, 0x572c83b8, 0x0, 0x2)
    /Users/rip/go/pkg/mod/gopkg.in/alecthomas/kingpin.v2@v2.2.6/app.go:222 +0x183
main.main()
    /Users/rip/go/src/github.com/nats-io/natscli/nats/main.go:109 +0x113b

[ripienaar]

While piping yes to the cli is neither useful or neccesary, I've made it exit with a less scary error in that case.

You can pass -f to avoid the prompt.

#153