Bug Report

Steps to reproduce

Run the following README.md:

# Heading 1 Test ## Heading 2 ### Heading 3A Lorem ipsum #### Heading 4A ##### Heading 5A Lorem ipsum ### Heading 3B Lorem ipsum #### Heading 4B <!-- {docsify-ignore} --> ##### Heading 5B Lorem ipsum

What is current behaviour

The sidebar does not show up and the console shows:

 ```docsify.min.js:1 Uncaught TypeError: Cannot read property 'level' of undefined at $n.sidebar (docsify.min.js:1) at Vn.Xn._renderSidebar (docsify.min.js:1) at Vn.Pn (docsify.min.js:1) at docsify.min.js:1 at o (docsify.min.js:1) at B (docsify.min.js:1) at t (docsify.min.js:1) at docsify.min.js:1 at docsify.min.js:1 at docsify.min.js:1 

What is the expected behaviour

Sidebar shows up

Other relevant information

• Bug does still occur when all/other plugins are disabled?

• Your OS: macOS Catalina

• Node.js version: 12.18.3

• npm/yarn version: 6.14.6

• Browser version: Chrome Version 84.0.4147.135 (Official Build) (64-bit)

• Docsify version: 4.11.6

• Docsify plugins: none

Please create a reproducible sandbox

Mention the docsify version in which this bug was not present (if any)