panic if decoding to an empty slice

[chowey]

Try the following code:

package main

import "github.com/BurntSushi/toml"
import "log

type Q struct {
    Test []string
}

func main() {
    q := Q{Test: []string{}}
    _, err := toml.Decode(`Test = ["test"]`, &q)
    if err != nil {
        log.Fatal(err)
    }
}

This results in a panic:

panic: reflect: slice index out of range

goroutine 1 [running]:
reflect.Value.Index(0x6c1b60, 0x12658d80, 0xd7, 0x0, 0x0, 0x0, 0x0)
        c:/go/src/reflect/value.go:818 +0x10f github.com/BurntSushi/toml.(*MetaData).unifySliceArray(0x12652ba0, 0x6c0d60, 0x12658dd0, 0x57, 0x6c1b60, 0x12658d80, 0xd7, 0x0, 0x0)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:321 +0xde github.com/BurntSushi/toml.(*MetaData).unifySlice(0x12652ba0, 0x6c0d60, 0x12658dd0, 0x6c1b60, 0x12658d80, 0xd7, 0x0, 0x0)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:314 +0x1b4
github.com/BurntSushi/toml.(*MetaData).unify(0x12652ba0, 0x6c0d60, 0x12658dd0, 0x6c1b60, 0x12658d80, 0xd7, 0x0, 0x0)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:206 +0xb11 github.com/BurntSushi/toml.(*MetaData).unifyStruct(0x12652ba0, 0x6cc160, 0x126543c0, 0x6d3e80, 0x12658d80, 0xd9, 0x0, 0x0)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:252 +0x65a github.com/BurntSushi/toml.(*MetaData).unify(0x12652ba0, 0x6cc160, 0x126543c0, 0
x6d3e80, 0x12658d80, 0xd9, 0x0, 0x0)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:200 +0xb9f github.com/BurntSushi/toml.Decode(0x7adf28, 0xf, 0x6bcbe0, 0x12658d80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        %GOPATH%/src/github.com/BurntSushi/toml/decode.go:114 +0x1c5 main.NewStaticContext(0x12655947, 0xa, 0x12656900, 0x0, 0x0, 0x0)
        ...

This is only caused when the Test field is initialized to an empty slice.

If Test is nil or has at least one element, Decode works as expected.