"There are multiple tabs open" warning improperly warns about closing tabs that will be restored
Open two Epiphany windows, one of which has multiple tabs. Focus the window with only a single tab open and press Ctrl+Q. You'll see the warning message added in !278 (merged), warning the user that all tabs will be lost.
Then proceed to close the window and reopen Epiphany. All tabs are restored, despite the warning.
We should only show this warning when closing a single window, not when closing the entire browser.