window might not be defined in node.js environment.

[BurkovBA]

Hi, I was trying to do server-side rendering of my React project, using metismenu.

It was a success, except by one problem: currently metismenu assumes that window object is available, while checking for window.QUnit object in tests. Thing is, in node.js environment window is undefined, thus this code is crashing.

So I did this tiny fix, checking if window is undefined. This will enable the use of metismenu on server side and make me (and hopefully other users) happy campers.

Please, bump package version and publish a patched NPM package, if you accept this PR.

Thanks and cheers!

[BurkovBA]

@onokumus Osman, could you publish the new version of this package, please? I'd like to serve the app from backend with it.

Thank you!