calcHash function: Don't crash when QString::null is passed.
calcHash function: Don't crash when QString::null is passed.

svn path=/trunk/KDE/kdepim/akregator/; revision=415644

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