Fix default: nil with fallbacks

lib/i18n/backend/fallbacks.rb

@@ -37,15 +37,16 @@ module Fallbacks
       def translate(locale, key, options = {})
         return super unless options.fetch(:fallback, true)
         return super if options[:fallback_in_progress]
-        default = extract_non_symbol_default!(options) if options[:default]
+        original_default = options[:default]
+        extract_non_symbol_default!(options)
 
         begin
           options[:fallback_in_progress] = true
           I18n.fallbacks[locale].each do |fallback|
             begin
               catch(:exception) do
                 result = super(fallback, key, options)
-                return result if (result.nil? && options.key?(:default) && options[:default].nil?) || !result.nil?
+                return result unless result.nil?
               end
             rescue I18n::InvalidLocale
               # we do nothing when the locale is invalid, as this is a fallback anyways.
@@ -55,7 +56,7 @@ def translate(locale, key, options = {})
           options.delete(:fallback_in_progress)
         end
 
-        return super(locale, nil, options.merge(:default => default)) if default
+        return super(locale, nil, options.merge(:default => original_default)) if options.key?(:default)
         throw(:exception, I18n::MissingTranslation.new(locale, key, options))
       end
 

test/backend/fallbacks_test.rb

@@ -59,6 +59,11 @@ def setup
     assert_equal({}, I18n.t(:missing_bar, :locale => :'de-DE', :default => {}))
   end
 
+  test "returns the :de translation for a missing :'de-DE' when :default is nil" do
+    assert_equal 'Bar in :de', I18n.t(:bar, :locale => :'de-DE', :default => nil)
+    assert_nil I18n.t(:missing_bar, :locale => :'de-DE', :default => nil)
+  end
+
   test "returns the :'de-DE' default :baz translation for a missing :'de-DE' when defaults contains Symbol" do
     assert_equal 'Baz in :de-DE', I18n.t(:missing_foo, :locale => :'de-DE', :default => [:baz, "Default Bar"])
   end