UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36

Steps to reproduce the problem:
1. start google chrome on linux and on mac os - do the same actions on both google chrome
2. install silver bird plus extension - https://chrome.google.com/webstore/detail/silver-bird-plus-twitter/kagejfgngcmkbaacpmcnbpkhmhoeccee
3. activate it (authorize it to allow access your twitter feed)
4. click on silverbird icon - list of tweets will show
5. click on any URL using MIDDLE MOUSE button

What is the expected behavior?
1) silver bird screen will stay on screen
2) url will open in new tab in background

What went wrong?
On Linux - behaves as expected, silverbird window stays on screen
On Mac OS X/Windows - url is open in new tab in background BUT silver bird screen gets closed while it should stay on screen

That's different behaviour on Mac OS X (bad) than on Linux (good).

Did this work before? N/A 

Chrome version: 68.0.3440.106  Channel: stable
OS Version: OS X 10.13.6
Flash Version: 

Note: clicking on URL with middle button opens URL in new tabs twice - it's extension bug that doesn't matter for this issue