crash when missing glob pattern

[yarbelk]

$ es dec --region ap-southeast-1 -- `which ep`  -- `which cat` *.env
panic: runtime error: index out of range

goroutine 1 [running]:
panic(0x57a020, 0xc420010250)
        /usr/lib/go/src/runtime/panic.go:500 +0x1a1
github.com/spf13/cobra.(*Command).ExecuteC(0xc4200ae240, 0x5a6859, 0xf, 0xc42007a46a)
        /home/me/go/src/github.com/spf13/cobra/command.go:671 +0x7b6
github.com/spf13/cobra.(*Command).Execute(0xc4200ae240, 0x5a500e, 0x7)
        /home/me/go/src/github.com/spf13/cobra/command.go:648 +0x2b
main.main()
        /home/me/go/src/github.com/kreuzwerker/envplate/bin/ep.go:71 +0x51d