Vertical tab, moving sidebar button to overflow menu will disable button

Steps:

1. Vertical tab mode
2. Right click sidebar button and move to overflow menu

The end result:

Should be one of following:

• This is not allowed, remove the option (it is not available in horizontal mode anyway)
• Sidebar button works inside overflow menu

PS: Related to #7847 ?

Version 0.99.132.2-rc (WebKit 621.1.2.111.4)

Sequoia (15)