Fix Dependencies watch_frames collection. [#24 state:resolved]

Previously, the code collecting watch_frames could fail leaving
watch_frames defined but nil. The cleanup code checks watch_frames
is defined, but not that it holds a value, raising an undefined method
on NilClass error rather than the original cause.  This can make
debugging the underlying cause a total pain.

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

activesupport/lib/active_support/dependencies.rb

@@ -384,7 +384,7 @@ def new_constants_in(*descs)
     return new_constants
   ensure
     # Remove the stack frames that we added.
-    if defined?(watch_frames) && ! watch_frames.empty?
+    if defined?(watch_frames) && ! watch_frames.blank?
       frame_ids = watch_frames.collect(&:object_id)
       constant_watch_stack.delete_if do |watch_frame|
         frame_ids.include? watch_frame.object_id

activesupport/test/dependencies_test.rb

@@ -584,6 +584,12 @@ def test_new_constants_in_with_inherited_constants
     assert_equal [], m
   end
 
+  def test_new_constants_in_with_illegal_module_name_raises_correct_error
+    assert_raises(NameError) do
+      Dependencies.new_constants_in("Illegal-Name") {}
+    end
+  end
+
   def test_file_with_multiple_constants_and_require_dependency
     with_loading 'autoloading_fixtures' do
       assert ! defined?(MultipleConstantFile)