[0.7.2 regression] Outputs multiple empty lines on <enter>

[pjg]

Here's my guard-shell config (https://github.com/pjg/dotfiles/blob/master/.Guardfile#L38-L51):

  guard 'shell' do
    # Restart application server
    watch('Gemfile.lock')                       { |_| `touch tmp/restart.txt` }
    watch(%r{^lib/.*})                          { |_| `touch tmp/restart.txt` }
    watch('config/environments/development.rb') { |_| `touch tmp/restart.txt` }
    watch(%r{^config/locales/.+\.yml$})         { |_| `touch tmp/restart.txt` }
    watch('config/application.yml')             { |_| `touch tmp/restart.txt` }
    watch('config/secrets.yml')                 { |_| `touch tmp/restart.txt` }
    watch('config/settings.yml')                { |_| `touch tmp/restart.txt` }
    watch('config/settings.local.yml')          { |_| `touch tmp/restart.txt` }
    watch(%r{^config/initializers/.+\.rb$})     { |_| `touch tmp/restart.txt` }
  end

When I press <enter> in guard console, it prints 9 newlines:

It wasn't the case with 0.7.1.