patch applied (cabal-install): Workaround for 'cabal install world' problem with empty world file

[Duncan Coutts]

Sun May  9 20:30:51 PDT 2010  Duncan Coutts <duncan at haskell.org>
  * Workaround for 'cabal install world' problem with empty world file
  The current dep resolver does not like an empty set of targets
  along with a non-empty set of constraints.

    M ./Distribution/Client/Dependency.hs -1 +6

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=cabal-install;a=darcs_commitdiff;h=20100510033051-adfee-f8b20ab260a7373676e7aef51e4328e40077bd68.gz