TOC becomes ugly if some heading level is missing

[elimohl]

# First
### Third

becomes

   * [First](#first)
         * [Third](#third)

and github renders it in one line (see https://github.com/elimohl/test/blob/master/README.md)

[ekalinin]

Hey @elimohl

Thanks for report.

But what can i do if the origin text has missed headings?

[elimohl]

Maybe add fictional heading or treat inner headings as their level is less. Or at least add a warning about this behavior.