fix typo "QString:: null" -> QString()
fix typo "QString:: null" -> QString()

svn path=/trunk/KDE/kdepim/; revision=1029661

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi