From cfc355c006a3f531e4024e4cd54cbc4740f8635a Mon Sep 17 00:00:00 2001
From: David Mike Simon <david.mike.simon@gmail.com>
Date: Mon, 18 Jun 2012 19:40:48 -0700
Subject: [PATCH] Fix for issue 560 where joins could be thrown away by
 ActiveRecordAdapter::merge_joins

---
 lib/cancan/model_adapters/active_record_adapter.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/cancan/model_adapters/active_record_adapter.rb b/lib/cancan/model_adapters/active_record_adapter.rb
index f20da17..d7d856f 100644
--- a/lib/cancan/model_adapters/active_record_adapter.rb
+++ b/lib/cancan/model_adapters/active_record_adapter.rb
@@ -145,8 +145,8 @@ module CanCan
       # Takes two hashes and does a deep merge.
       def merge_joins(base, add)
         add.each do |name, nested|
-          if base[name].is_a?(Hash) && !nested.empty?
-            merge_joins(base[name], nested)
+          if base[name].is_a?(Hash)
+            merge_joins(base[name], nested) unless nested.empty?
           else
             base[name] = nested
           end