Publishing membership has no effect because already used pseudonym

Yesterday a user was trying to publish her candidature directly from her simple cesium account but she was choosing the pseudonym "isa" or "isabel" which cesium was showing that it was available (green icon) and letting her clicking the Next button...

Problem was that after the confirm dialog, she was returning to her simple account with no effect. We realized that Cesium was showing "pseudonim is available" even if the Directory was showing that it was already taken... after realizing, she choosed a more complex one and then Cesium worked fine transforming the account into a member one...

Tested with latest 1.6.12 in chrome and android app. Thanks for checking.