port from enterprise: fix crash when editing toolbars while a plugin without part is active
port from enterprise: fix crash when editing toolbars while a plugin without part is active

svn path=/branches/KDE/3.5/kdepim/; revision=675061

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