Fixed crash resulting from trying to berserk

unsuccessful summons. (Brothers in Arms)

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@1972 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on August 5, 2007
7BQVRR4GR2WNIGOE7D6WGVSFLMW5B6HPMJIZPZBPTSM6H57XXH4AC
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