sferik/rails_admin — pull request #2079 by nathanl (2014-10-06 20:03:53+00:00)
Title: Friendlier error if filter is not found

If user sets, e.g., `filters [:name, :manager]`,
and manager is not set to `filterable true`,
RailsAdmin currently raises a NoMethodError
when trying to call `.type` on nil.

This change raises a more descriptive error
to help the user find the problem