Fix Vampiric Drain backlash check.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@9438 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dolorous  on March 13, 2009
6O47K6HB324PF6GFUVSE7W6AE2DFITU6ZTM5VJGT3PXSTCLAHXOQC
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