Merge pull request #135918 from MarcosDaNight/fix/kubectl-exec-panic

kubectl: Fix panic in exec terminal size queue

staging/src/k8s.io/kubectl/pkg/cmd/exec/exec.go

@@ -411,6 +411,10 @@ type terminalSizeQueueAdapter struct {
 }
 
 func (a *terminalSizeQueueAdapter) Next() *remotecommand.TerminalSize {
+	if a.delegate == nil {
+		return nil
+	}
+
 	next := a.delegate.Next()
 	if next == nil {
 		return nil