rails/rails — pull request #5210 by Pliny (2012-02-28 18:24:18+00:00)
Title: Fix for #5200

reset_counters() was crashing when there were multiple belongs_to associations with the same foreign key.. with only one of the belongs_to associations having a custom counter_cache.

reset_counters() made the false assumption that each belongs_to association has a counter_cache.