calcHash function: Don't crash on null strings
calcHash function: Don't crash on null strings

svn path=/branches/KDE/3.4/kdepim/; revision=415664

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