Panic when TOC rendering.

[odknt]

A content for reproduce in the following.

= sect0
:toc:

level 1 sections not exists.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x6bcdde]

goroutine 1 [running]:
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.renderTableOfContents(0xc0001674a0, 0x739d80, 0x3074636573, 0x1, 0x1, 0xc0001c14b0)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/table_of_contents.go:56 +0x9e
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.renderElement(0xc0001674a0, 0x731e20, 0xc215f0, 0x1, 0x1, 0xc05b40, 0x7f5f64039440, 0x0)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/renderer.go:79 +0x13ce
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.renderElements(0xc0001674a0, 0xc0001d4120, 0x3, 0x3, 0x1, 0x5, 0x40, 0x0, 0x0)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/renderer.go:26 +0x124
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.renderDocumentElements(0xc0001674a0, 0xc0001d40f0, 0xc0001d4120, 0x3, 0x3, 0xc0001d4150, 0xc215f0, 0x0, 0x0, 0xc0001d4180, ...)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/document.go:123 +0xe1
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.renderDocument(0xc0001674a0, 0x7e5880, 0xc00009e008, 0x0, 0xc0001674a0, 0xc0001d41b0)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/document.go:96 +0x221
github.com/bytesparadise/libasciidoc/pkg/renderer/html5.Render(0xc0001674a0, 0x7e5880, 0xc00009e008, 0xc0001d4120, 0x3, 0x3)
        /go/src/github.com/bytesparadise/libasciidoc/pkg/renderer/html5/renderer.go:16 +0x3f
github.com/bytesparadise/libasciidoc.convertToHTML(0x7e6f40, 0xc00009a010, 0xc0001d40f0, 0xc0001d4120, 0x3, 0x3, 0xc0001d4150, 0xc215f0, 0x0, 0x0, ...)
        /go/src/github.com/bytesparadise/libasciidoc/libasciidoc.go:62 +0x105
github.com/bytesparadise/libasciidoc.ConvertToHTML(0x7e6f40, 0xc00009a010, 0x7e5860, 0xc00015a220, 0x7e5880, 0xc00009e008, 0xc0001c1c90, 0x1, 0x1, 0xc000127bc8, ...)
        /go/src/github.com/bytesparadise/libasciidoc/libasciidoc.go:57 +0x3d0
github.com/bytesparadise/libasciidoc.ConvertFileToHTML(0x7e6f40, 0xc00009a010, 0x7fff8a228b03, 0xe, 0x7e5880, 0xc00009e008, 0xc000127c90, 0x1, 0x1, 0x0, ...)
        /go/src/github.com/bytesparadise/libasciidoc/libasciidoc.go:37 +0x116
main.NewRootCmd.func1(0xc000198000, 0xc000163180, 0x1, 0x4, 0x0, 0x0)
        /go/src/github.com/bytesparadise/libasciidoc/cmd/libasciidoc/root_cmd.go:37 +0x295
github.com/spf13/cobra.(*Command).execute(0xc000198000, 0xc0000a4010, 0x4, 0x4, 0xc000198000, 0xc0000a4010)
        /go/pkg/mod/github.com/spf13/[email protected]/command.go:762 +0x473
github.com/spf13/cobra.(*Command).ExecuteC(0xc000198000, 0x1, 0x0, 0xc000198280)
        /go/pkg/mod/github.com/spf13/[email protected]/command.go:852 +0x2fd
github.com/spf13/cobra.(*Command).Execute(0xc000198000, 0xc000127f70, 0x1)
        /go/pkg/mod/github.com/spf13/[email protected]/command.go:800 +0x2b
main.main()
        /go/src/github.com/bytesparadise/libasciidoc/cmd/libasciidoc/main.go:17 +0x97

[xcoulon]

thanks for reporting this issue @odknt. I'll take care of it.