Fix generating params with optional defaults [#3404 state:resolved]

actionpack/lib/action_dispatch/routing/deprecated_mapper.rb

@@ -175,7 +175,7 @@ def optionalize_trailing_dynamic_segments(path, requirements, defaults) #:nodoc:
               optional = false
             elsif segment =~ /^:(\w+)$/
               if defaults.has_key?($1.to_sym)
-                defaults.delete($1.to_sym)
+                defaults.delete($1.to_sym) if defaults[$1.to_sym].nil?
               else
                 optional = false
               end

actionpack/test/controller/routing_test.rb

@@ -1639,9 +1639,7 @@ def test_generate_with_default_params
       map.connect ':controller/:action/:id'
     end
 
-    pending do
-      assert_equal '/ibocorp', set.generate({:controller => 'ibocorp', :page => 1})
-    end
+    assert_equal '/ibocorp', set.generate({:controller => 'ibocorp', :page => 1})
   end
 
   def test_generate_with_optional_params_recalls_last_request