Closing server buffer while disconnected does not close opened autojoin channel buffers

[ghost]

If I have a server with autojoin configured and I close the server buffer while disconnected, the associated channel buffers are not closed.

Steps to reproduce:

1. /server add example irc.example.invalid -autojoin=#example
2. /connect example
3. /close the server buffer

The #example buffer is opened before connection but it is not closed when the server buffer is closed.

WeeChat version: 1.6