Make possible to unset virtual-mailboxes

[drym3r]

Problem

I'm trying to use multiple accounts on mutt. I do that using a couple of folder-hooks like this:

macro index,pager <f3> '<sync-mailbox><enter-command>source ~/.mutt/[email protected]<enter><change-folder>!<enter>'

When I execute that macro, it keeps sourcing that file, but the virtual-mailboxes are appended and not substituted.

Feature request

This could be prevented if it could be posible to initialize virtual-mailboxes to an empty string, for example. Something like unset mailboxes on regular mutt.

Thanks for all your work, the notmuch patch really makes mutt cool.