rails/rails — pull request #12925 by akshay-vishnoi (2013-11-17 11:19:44+00:00)
Title: #compute_asset_host - return nil if host is not defined

`compute_asset_host` may raise `NameError` exception when
1. `config.asset_host` is not defined, and
2. `request` is not set OR `options[:protocol]` is other than `:request`