Ext.ux.grid has no properties error

Problem
Trying to use ExtJS with RubyOnRails on Heroku, gives the following error and a blank page in Firebug.

Solution
In Heroku, you will probably have to manually upload the files from the ExtJS library, as well as the ext_scaffold plugin.
When you do that, two files that ext_scaffold needs, and which they should be located in ext_scaffold/assets/javascripts should be copied to public/javascripts.
The files are: