The "Middle-click on bookmarks" preference does not have any effect

[piroor]

Reported on the full review.

The "Middle-click on bookmarks" preference does not have any effect for me.
Steps to reproduce:
1. Visit about:addons
2. Open the preferences for your add-on.
3. Select "Load into the current tab" (for "Middle-click on bookmarks") and close the preferences,
4. Click on the bookmarks menu, and middle-click on any bookmark in the menu.
5. Click on the bookmarks menu and check "View Bookmarks sidebar".
6. Middle-click on any bookmark in the sidebar.

After step 4 and after step 6, I expected the bookmark to open in the current tab, but it opened in a new tab instead.

Please address this in the next update.

Tested on Linux with Firefox 44.0