The links from a split tab are no longer loaded after you open a link in a new tab

[Softvision-CristinaBadescu]

[Affected versions]:

• Nightly 60.0a1
• Tab Split 0.1.8

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a clean Firefox profile with the latest Tab Split v0.1.8 installed.
• Have one tab open.

[Steps to reproduce]:

1. Open Firefox browser with the profile from prerequisites.
2. Click the "Tab Split" button and navigate to a website.
3. Open a link in a new tab.
4. Click a hyperlinked element and observe the behavior.

[Expected result]:

• The page is loaded.

[Actual result]:

• The page is not loaded and only some hyperlinked elements are clickable.

[Notes]:

• You can no longer focus the 1st tab if you click the page's content and also you can no longer access hyperlinked elements from it.
• When you click a hyperlinked element, the link isn't loaded in the focused tab, but in the other opened tab.
• This issue is also reproducible for links opened from "about:newtab" page. All the future "about:newtab" pages are affected (even if they are not opened in a split) if you open a link in a new tab from it.
• This issue is no longer reproducible after you click the new opened tab.
• This issue is no longer reproducible if you refresh the tab.
• If you open a new link from the 1st tab, you will encounter this issue The split tabs are wrongly separated if you use "Open Link in a New Tab" option from the 1st split tab #59.
• Here is a screen recording with this issue:
  

[ianb]

So this seems to be specifically about opening a new tab in the background (via context menu or Cmd-click). It's a little hard for me to tell, but I think clicks actually go to that new tab. When I click around on a page I can see the new tab's title change, even though the current tab appears to be in focus.

I've also confirmed this on the bootstrap version of the add-on.

Nothing messages appear in the browser console.