SIGSEGV thrown often from Spinner and Progress release terminal procedure

[cardil]

SIGSEGV is thrown quite often from:

client-pkg/pkg/output/tui/spinner.go

Lines 93 to 95 in ca2b56e

	if term.IsWriterTerminal(out) {
	_ = t.ReleaseTerminal()
	}

Here's goroutines dump:

$ go run github.com/cardil/repro-kn-cli-bad-license@latest
Loading... Done
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x569e90]

goroutine 6 [running]:
github.com/charmbracelet/bubbletea.(*Program).ReleaseTerminal(0xc000189450)
	/home/ksuszyns/.gvm/pkgsets/go1.21.4/global/pkg/mod/github.com/charmbracelet/bubbletea@v0.25.0/tea.go:651 +0x30
knative.dev/client-pkg/pkg/output/tui.(*BubbleSpinner).start.func1()
	/home/ksuszyns/.gvm/pkgsets/go1.21.4/global/pkg/mod/knative.dev/client-pkg@v0.0.0-20240326133606-ca64d2dc74eb/pkg/output/tui/spinner.go:94 +0xa5
created by knative.dev/client-pkg/pkg/output/tui.(*BubbleSpinner).start in goroutine 1
	/home/ksuszyns/.gvm/pkgsets/go1.21.4/global/pkg/mod/knative.dev/client-pkg@v0.0.0-20240326133606-ca64d2dc74eb/pkg/output/tui/spinner.go:87 +0x396
exit status 2

/kind bug