This report has been filled here:

https://bugs.launchpad.net/ubuntu/+source/evolution/+bug/157718

"
1) start evolution
2) select a message
3) right-click->create rule from message->search folder from sender
4) set "Search name" to "/."
        (leaving all the rest at default:
                no threads,
                specific folder: mbox:inbox)
5) "OK"

The "Search Folders" tree now contains an unnamed folder with a sub-folder named "."

I tried to bring up the properties on the unnamed folder and got an
error message:
        Cannot edit Search Folder "vfolder:/home/thomas/.evolution/mail/
                vfolder;noselect=yes#" as it does not exist'''

Properties on the "." folder list its "Search name" as "/."
The folder contains the expected emails.

After re-starting evolution the "Search Folders" tree now contains:
home->thomas->.evolution->mail->vfolder

All these folders are empty, bringing up the properties on them results in the same error message as above.
I can delete these folders, but they reappear instantly whenever I select the unnamed folder (though not when I select the "." folder)."