Fixed Class.remove to not blow up on inheritance

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3532 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/lib/active_support/core_ext/class/removal.rb

@@ -11,12 +11,12 @@ def remove_class(*klasses)
     klasses.each do |klass|
       # Skip this class if there is nothing bound to this name
       next unless defined?(klass.name)
-      
+    
       basename = klass.to_s.split("::").last
       parent = klass.parent
-      
+    
       # Skip this class if it does not match the current one bound to this name
-      next unless klass = parent.const_get(basename)
+      next unless parent.const_defined?(basename) && klass = parent.const_get(basename)
 
       parent.send :remove_const, basename unless parent == klass
     end