here's my setup:
where LocalizedValue is:
I create one Product assign two values for it's description (first entry is <Locale.ENGLISH, null> and the second is <Locale.GERMAN, "test">). Then I select the product from the database, and inspect the description map - the result is it only has 1 element in the map - <Locale.GERMAN, "test"> one.
I will create a test project soon.