[sylpheed:35219] Cannot delete a folder from gui

[Dennis Carr]

Runnin Debian Linux, stable, compiled version of Sylpheed 3.1.4.

I currently have an old IMAP folder tree in my folders, but it is not
associated with an account.  I seem to be unable to remove said tree,
as well, with the usual method of right-click and selecting delete
(the delete option is not available). Any time I attempt to left-click
on a folder within, Sylpheed tells me it could not establish a
connection with the server.

I'm guessing that I had removed the account related to this, but the
tree did not get taken with it.

So all this said, how do I remove this folder tree so as I can get it
out of the way?

-Dennis