Sidebar links not highlighted, history back button, Cyrillic headers

[abernov]

• I confirm that this is an issue rather than a question.

Bug report

Steps to reproduce

1. Add this header to some md-file:
   '## Header not highlighted! Cyrillic char ф'
2. In browser, in sidebar click this header link and other links.
3. Click several times browser history back button.

What is expected?

Sidebar active link will be highlighted green.

What is actually happening?

All links highlighted, but not this!

Other relevant information

• Output of npx vuepress info in my VuePress project:

System:
OS: Windows 10
CPU: (4) x64 Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz
Binaries:
Node: 11.15.0 - C:\Program Files (x86)\Nodist\bin\node.EXE
Yarn: 1.9.4 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.7.0 - C:\Program Files (x86)\Nodist\bin\npm.EXE
Browsers:
Google Chrome: Version 78.0.3904.70 (Official Build) (64-bit)
npmPackages:
@vuepress/core: Not Found
@vuepress/theme-default: Not Found
vuepress: ^1.2.0 => 1.2.0
npmGlobalPackages:
vuepress: Not Found