Error upgrading vim

gistfile1.txt

[~] ➔ brew doctor
Your system is raring to brew.

[~] ➔ HOMEBREW_MAKE_JOBS=1 VERBOSE=1 brew upgrade
==> Upgrading vim
ln -s ../Cellar/vim/7.3.666/bin/xxd xxd
ln -s ../Cellar/vim/7.3.666/bin/vimtutor vimtutor
ln -s ../Cellar/vim/7.3.666/bin/vimdiff vimdiff
ln -s ../Cellar/vim/7.3.666/bin/vim vim
ln -s ../Cellar/vim/7.3.666/bin/view view
ln -s ../Cellar/vim/7.3.666/bin/rvim rvim
ln -s ../Cellar/vim/7.3.666/bin/rview rview
ln -s ../Cellar/vim/7.3.666/bin/ex ex
ln -s ../Cellar/vim/7.3.666/share/vim vim
ln -s ../../../Cellar/vim/7.3.666/share/man/man1/xxd.1 xxd.1
ln -s ../../../Cellar/vim/7.3.666/share/man/man1/vimtutor.1 vimtutor.1
ln -s ../../../Cellar/vim/7.3.666/share/man/man1/vimdiff.1 vimdiff.1
ln -s ../../../Cellar/vim/7.3.666/share/man/man1/vim.1 vim.1
ln -s ../../../Cellar/vim/7.3.666/share/man/man1/evim.1 evim.1
ln -s ../../Cellar/vim/7.3.666 vim
ln -s ../Cellar/vim/7.3.666 vim
Error: can't convert nil into String
Please report this bug:
    https://github.com/mxcl/homebrew/wiki/bug-fixing-checklist
/usr/local/Library/Homebrew/download_strategy.rb:466:in `file?'
/usr/local/Library/Homebrew/download_strategy.rb:466:in `fetch'
/usr/local/Library/Homebrew/formula.rb:572:in `fetch'
/usr/local/Library/Homebrew/formula.rb:583:in `stage'
/usr/local/Library/Homebrew/formula.rb:219:in `brew'
/usr/local/Library/Homebrew/build.rb:114:in `install'
/usr/local/Library/Homebrew/build.rb:42:in `main'
/usr/local/Library/Homebrew/build.rb:12
/usr/local/Library/Formula/vim.rb:12