The discussion is here :
http://www.wikidata.org/wiki/Wikidata:Contact_the_development_team#Can.27t_delete_languages_from_an_item

Problem :
When I add an alias, a variable is created but when I throw the delete flag for an alias and if there is no more aliases for this language the variable is still alive but empty. It's why we can see on labelLister, which use json format, blank rows in some language

Version: unspecified
Severity: normal
URL: http://www.wikidata.org/w/api.php?format=jsonfm&action=wbgetentities&ids=Q853475