Fix CSV import for vocabularies

One or more exceptions caught, see full set in UmbrellaException#getCauses

Uncaught exception: com.google.gwt.event.shared.UmbrellaException: One or more exceptions caught, see full set in UmbrellaException#getCauses
    at Unknown.re(Unknown Source)
    at Unknown.mj(Unknown Source)
    at Unknown.iz(Unknown Source)
    at Unknown.lz(Unknown Source)
    at Unknown.Hy(Unknown Source)
    at Unknown.ytb(Unknown Source)
    at Unknown.XDb(Unknown Source)
    at Unknown.Eib(Unknown Source)
    at Unknown.Qib(Unknown Source)
    at Unknown.Ug(Unknown Source)
    at Unknown.anonymous(Unknown Source)
    at Unknown.Tj(Unknown Source)
    at Unknown.Wj(Unknown Source)
    at Unknown.anonymous(Unknown Source)
    at Unknown.anonymous(Unknown Source)
Caused by: com.google.gwt.json.client.JSONException: Unexpected typeof result 'xml'; please report this bug to the GWT team
    at Unknown.qe(Unknown Source)
    at Unknown.xe(Unknown Source)
    at Unknown.lj(Unknown Source)
    at Unknown.VF(Unknown Source)
    at Unknown.DG(Unknown Source)
    at Unknown.AG(Unknown Source)
    at Unknown.BG(Unknown Source)
    at Unknown.jSd(Unknown Source)
    at Unknown.aEb(Unknown Source)
    at Unknown.Uy(Unknown Source)
    at Unknown.Hy(Unknown Source)
    at Unknown.ytb(Unknown Source)
    at Unknown.XDb(Unknown Source)
    at Unknown.Eib(Unknown Source)
    at Unknown.Qib(Unknown Source)
    at Unknown.Ug(Unknown Source)
    at Unknown.anonymous(Unknown Source)
    at Unknown.Tj(Unknown Source)
    at Unknown.Wj(Unknown Source)
    at Unknown.anonymous(Unknown Source)
    at Unknown.anonymous(Unknown Source)