Prospective build fix after commit f8dbed12266c42785c1e4758eed05833ec035f33 in qtbase

Pass through the QVariant argument provided by the caller (QInputMethod).

Change-Id: Ia99546cd16287c14ce414d6aad0ea04488e7c6e2
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>