crash on invalid shell format input

[redbaron]

Describe the bug
SIGSEGV on invalid shell input format

Version of yq: 4.45.1
Operating system: mac
Installed via: home-brew

Command
The command you ran:

echo 'a\nb' | yq -p shell

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x1010847f8]

goroutine 1 [running]:
github.com/mikefarah/yq/v4/cmd.configureDecoder(0x0)
	github.com/mikefarah/yq/v4/cmd/utils.go:118 +0x48
github.com/mikefarah/yq/v4/cmd.evaluateSequence(0x140001c4008, {0x14000156860, 0x0, 0x2})
	github.com/mikefarah/yq/v4/cmd/evaluate_sequence_command.go:112 +0x278
github.com/mikefarah/yq/v4/cmd.New.func1(0x140001c4008?, {0x14000156860?, 0x4?, 0x101086cc9?})
	github.com/mikefarah/yq/v4/cmd/root.go:66 +0x74
github.com/spf13/cobra.(*Command).execute(0x140001c4008, {0x140001183a0, 0x2, 0x2})
	github.com/spf13/cobra@v1.8.1/command.go:985 +0x834
github.com/spf13/cobra.(*Command).ExecuteC(0x140001c4008)
	github.com/spf13/cobra@v1.8.1/command.go:1117 +0x344
github.com/spf13/cobra.(*Command).Execute(0x14000179f38?)
	github.com/spf13/cobra@v1.8.1/command.go:1041 +0x1c
main.main()
	github.com/mikefarah/yq/v4/yq.go:22 +0x1a0

Additional context