Bug with '#' if editing with TOC enabled

[Tattomoosa]

When Vue-Markdown is previewing a textarea that is being edited with the toc enabled, it throws an error when inputting # without a title after it.

This crashes the implementation in the live demo (markdown stops updating), but in my app it actually keeps working and just keeps throwing errors into the console.

Uncaught TypeError: Cannot read property 'type' of undefined
at Array.<anonymous> (vue-markdown.min.js:4)
at n.process (vue-markdown.min.js:2)
at s.parse (vue-markdown.min.js:1)
at s.render (vue-markdown.min.js:1)
at C (vue-markdown.min.js:1)
at VueMarkdown.<anonymous> (vue-markdown.min.js:1)
at Watcher.run (vue.js:3251)
at runBatcherQueue (vue.js:2984)
at Array.flushBatcherQueue (vue.js:2958)
at MutationObserver.nextTickHandler (vue.js:434)

To reproduce, turn on toc in the live demo

[onedou]

This issue is the same as mine

[onedou]

[beebase]

+1

[zoi-aoba]

me too

[fangbinwei]

I have the same problem. maybe toc should skip this situation?