panic in wkt.Unmarshal

[sosiska]

Hello! I found a panic in the wkt.Unmarshal function.

Problem
Panic occurs when using the wkt.Unmarshal function from orb/encoding/wkt package.

How to reproduce

package main

import (
	"fmt"
	"os"

	"github.com/paulmach/orb/encoding/wkt"
)

func main() {
	input := "LINESTRING"
	geom, err := wkt.Unmarshal(input)
	if err != nil {
		fmt.Printf("can't unmarshal: %v\n", err)
		os.Exit(0)
	}
	fmt.Printf("unmarshaled geom: %v\n", geom)
}

Expected behavior
I expect to get something like an invalid format error, or at least a panic with a message, like:

can't unmarshal: incorrect WKT format

Current behavior

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
github.com/paulmach/orb/encoding/wkt.trimSpaceBrackets({0x0?, 0xa?})
        /home/kirill/go/pkg/mod/github.com/paulmach/[email protected]/encoding/wkt/unmarshal.go:125 +0x9c
github.com/paulmach/orb/encoding/wkt.Unmarshal({0x4a26bf?, 0x53a780?})
        /home/kirill/go/pkg/mod/github.com/paulmach/[email protected]/encoding/wkt/unmarshal.go:256 +0x4df
main.main()
        /home/kirill/go/src/github.com/sosiska/wkt/main.go:12 +0x29

Process finished with the exit code 2