webapp: rake assets:precompile: undefined method `directory?' for nil:NilClass (leap_platfrom master branch)

from leap_platform master branch:

...
   - [web1] notice: /Stage[main]/Site_webapp/Exec[bundler_update]/returns: executed successfully
   - [web1] notice: /Stage[main]/Site_webapp/Exec[bundler_update]: Triggered 'refresh' from 1 events
   - [web1] notice: /Stage[main]/Site_webapp::Couchdb/Exec[migrate_design_documents]/returns: executed successfully
   - [web1] err: /Stage[main]/Site_webapp/Exec[compile_assets]/returns: change from notrun to 0 failed: /bin/bash -c "/usr/bin/bundle exec rake assets:precompile" returned 1 instead of one of [0] at /srv/leap/puppet/modules/site_webapp/manifests/init.pp:70
...

root@web1:~# su - leap-webapp
$ bash
leap-webapp@web1:~$ cd /srv/leap/webapp
leap-webapp@web1:~$ /bin/bash -c "/usr/bin/bundle exec rake assets:precompile
> ^C
leap-webapp@web1:~$ /bin/bash -c "/usr/bin/bundle exec rake assets:precompile"
/usr/bin/ruby1.9.1 /srv/leap/webapp/vendor/bundle/ruby/1.9.1/bin/rake assets:precompile:all RAILS_ENV=production RAILS_GROUPS=assets
rake aborted!
undefined method `directory?' for nil:NilClass
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:189:in `block in each_entry'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:185:in `each'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:185:in `each_entry'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:204:in `block in each_file'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:203:in `each'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:203:in `each_file'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/sprockets-2.2.2/lib/sprockets/base.rb:217:in `each_logical_path'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/static_compiler.rb:18:in `compile'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:56:in `internal_precompile'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:70:in `block (3 levels) in '
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:60:in `block (3 levels) in '
Tasks: TOP => assets:precompile:primary
(See full trace by running task with --trace)
rake aborted!
Command failed with status (1): [/usr/bin/ruby1.9.1 /srv/leap/webapp/vendor...]
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:12:in `ruby_rake_task'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:21:in `invoke_or_reboot_rake_task'
/srv/leap/webapp/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.14/lib/sprockets/assets.rake:29:in `block (2 levels) in '
Tasks: TOP => assets:precompile
(See full trace by running task with --trace)

(from redmine: created on 2013-08-03, closed on 2013-08-13, relates #3201 (closed))