Panic when calling Screen.Fini() while suspended

[rivo]

First of all, thanks for implementing #194!

I'd like to be able to stop the application after having called Screen.Suspend(), i.e. while the screen is suspended. Currently, calling Screen.Fini() results in a panic:

panic: close of nil channel
github.com/gdamore/tcell/v2.(*tScreen).disengage(0xc000182000)
        /usr/local/var/go/pkg/mod/github.com/gdamore/tcell/v2@v2.2.0/tscreen_unix.go:66 +0x87
github.com/gdamore/tcell/v2.(*tScreen).finalize(...)
        /usr/local/var/go/pkg/mod/github.com/gdamore/tcell/v2@v2.2.0/tscreen_unix.go:111
github.com/gdamore/tcell/v2.(*tScreen).finish(...)
        /usr/local/var/go/pkg/mod/github.com/gdamore/tcell/v2@v2.2.0/tscreen.go:478
sync.(*Once).doSlow(0xc0001821b4, 0xc00017bc30)
        /usr/local/Cellar/go/1.15/libexec/src/sync/once.go:66 +0xec
sync.(*Once).Do(...)
        /usr/local/Cellar/go/1.15/libexec/src/sync/once.go:57
github.com/gdamore/tcell/v2.(*tScreen).Fini(0xc000182000)
        /usr/local/var/go/pkg/mod/github.com/gdamore/tcell/v2@v2.2.0/tscreen.go:473 +0x6a

Would it be possible for you to allow calling Fini() after Suspend() (without having to call Resume() first)?

[gdamore]

Yes, I don't see any reason we should not allow that. Its strictly an oversight that this was missed.

[gdamore]

I believe this should be fixed now as a consequence of fixing #460. disengage is now idempotent.

[rivo]

Thanks!