Fix bug in is_tried_type() which was crashing labyrinth generation.

I could've sworn that I'd fixed this already.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@1755 c06c8d41-db1a-0410-9941-cceddc491573

Created by  haranp  on July 5, 2007
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