[Evolution] Duplicated messages in search folders

[Jorge <jorge13515 gmail com>]

Hi.  I use Evolution 3.18.2 on Ubuntu 15.10 (with a few PPAs and other
extra repositories, including ppa:gnome3-team/gnome3 and
ppa:gnome3-team/gnome3-staging).
Some search folders show certain messages twice.  I provide links to
two screenshots:
1. evolution-edit-search-folder-screenshot.png shows the search folder
properties.
2. evolution-search-folder-screenshot-highlighted.png shows the search
folder with duplicated messages highlighted by color-coded arrows.

1: https://www.dropbox.com/s/j9luusb1f5gjgyj/evolution-edit-search-folder-screenshot.png?dl=0
2: https://www.dropbox.com/s/7e6lbgevwp4y729/evolution-search-folder-screenshot-highlighted.png?dl=0