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

svn path=/trunk/KDE/kdepim/kontact/src/; revision=675072

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