Another instance of !expr != foo; removed the double negative. Fixes

compile error, but I still think the logic is still incorrect; can someone check who knows the code better check this out?

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@3570 c06c8d41-db1a-0410-9941-cceddc491573

Created by  pauldubois  on March 9, 2008
L7G767VEPTZOILF3VTTKFAAZTJ4NPOLXCFUPF2FKJSGAGSUBW5NAC
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