Close button sends client to the tray, statically linked Qt for OSX.
See the Changelog for list of features and fixes currently only available in the nightly builds.
This is already a feature of SoulseekQt. Simply check the "Discard Repeated Results" box at the bottom of the wish list search results. Then close the window and those results from the user(s) should no longer appear.
i don't have that option on mine, i got 2014.1-31, i can disable wishlist searches.
n/m now i see it, i didn't have a pop a few minutes ago and now i see it.