Parsing error with two consecutive math blocks

[cowsed]

If the markdown source contains two consecutive math blocks, the parser will fail with a panic
https://go.dev/play/p/qvMPGNTfFXH

Source:

package main

import (
	"bytes"
	"fmt"

	mathjax "github.com/litao91/goldmark-mathjax"
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/renderer/html"
)

func main() {
	md := goldmark.New(
		goldmark.WithExtensions(mathjax.MathJax),
		goldmark.WithParserOptions(
			parser.WithAutoHeadingID(),
		),
		goldmark.WithRendererOptions(
			html.WithHardWraps(),
			html.WithXHTML(),
		),
	)

	var html bytes.Buffer
	mdContent := []byte(`
$$
1
$$
$$
2
$$
`)
	if err := md.Convert(mdContent, &html); err != nil {
		fmt.Println(err)
	}
	fmt.Println(html.String())
}

Result:

panic: interface conversion: interface {} is nil, not *mathjax.mathBlockData

goroutine 1 [running]:
github.com/litao91/goldmark-mathjax.(*mathJaxBlockParser).Continue(0xc00017c310?, {0x61c520, 0xc000116f80}, {0x61bbb8, 0xc00017c310}, {0x61bea0, 0xc00017c380})
	/tmp/gopath715487383/pkg/mod/github.com/litao91/[email protected]/block.go:47 +0x3b4
github.com/yuin/goldmark/parser.(*parser).parseBlocks(0xc000187508, {0x61c9a0, 0xc000190000}, {0x61bbb8, 0xc00017c310}, {0x61bea0, 0xc00017c380})
	/tmp/gopath715487383/pkg/mod/github.com/yuin/[email protected]/parser/parser.go:1093 +0x5b9
github.com/yuin/goldmark/parser.(*parser).Parse(0xc000187508, {0x61bbb8, 0xc00017c310}, {0x0, 0x0, 0x40ce05?})
	/tmp/gopath715487383/pkg/mod/github.com/yuin/[email protected]/parser/parser.go:876 +0x14b
github.com/yuin/goldmark.(*markdown).Convert(0xc000172200, {0xc000164090, 0x11, 0x11}, {0x61a838, 0xc0000a9170}, {0x0, 0x0, 0x0})
	/tmp/gopath715487383/pkg/mod/github.com/yuin/[email protected]/markdown.go:117 +0xce
main.main()
	/tmp/sandbox2467797471/prog.go:34 +0x345