Posts without title should be accessible

[stevenjoezhang]

What does it do?

Issue resolved: #4228
See also #3672

How to test

git clone -b revert-3672 https://github.com/hexojs/hexo.git
cd hexo
npm install
npm test

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[coveralls]

Coverage decreased (-0.02%) to 97.758% when pulling ff56409 on revert-3672 into e5e898c on master.

[SukkaW]

We should retain empty title behavior, as slug might not be needed for every one.

[luchaoqi]

We should retain empty title behavior, as slug might not be needed for every one.

Agreed but posts with the empty title are disappearing in the archives before which hexo will take the file name as default title.

[stevenjoezhang]

@luchaoqi Are you using hexo-theme-icarus? Please open an issue here: https://github.com/ppoffice/hexo-theme-icarus/issues

"Posts without title should be accessible." is required by hexo-theme-unit-test