Fix assert failure in QueryBuilder.
Fix assert failure in QueryBuilder.

svn path=/trunk/KDE/kdepim/; revision=713135

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