Should not throw error when files.length == 0

[mariodu]

Directory structure likes below:

tests/
    units/

In units, there isn't any file. When I use mocha to run this path, it throws can't resolve path, but glob(path) returns []. Maybe, it shouldn't throw error.

tests/
    units/
        lib-test.js

If directory structure likes above, it works well.

see pull request #2001

[drazisil]

Believe fixed by merged #2450, no activity in one year, closing