I found a simple solution and I'm posting it here...
Insert into config/application.rb
config.i18n.default_locale = :hr
config.i18n.available_locales = [:hr, :en]
config.i18n.fallbacks = [:en]
Remove or comment the following line from config/environments/production.rb
# config.i18n.fallbacks = true
or change it to:
config.i18n.fallbacks = [:en]