Raises a helpful error if someone uses through but the association does not exists or was not defined yet
Raises a helpful error if someone uses through but the association does not exists or was not defined yet

Signed-off-by: Andre Lewis <fe5ca681e45e814c85f57423534075a616e1473e@gmail.com>
geokit/geokit-rails,zeke/geokit-rails,bellycard/geokit-acts-as-mappable,BlinkerGit/geokit-rails,geokit/geokit-rails3,jlecour/geokit-rails,jensb/geokit-rails,Spindle-Inc/geokit-rails,kidzui/geokit-rails3,globalworks/geokit-rails3