Simplify callback handling.
Simplify callback handling.

Follow-up r19260.

* subversion/bindings/swig/ruby/svn/fs.rb
  (Svn::Fs::Root#replay): Use nil instead of dummy callback Proc.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion