Don't crash when changing from "Switch betwen views with tabs" to "Merge all calendars into one view" when there aren't any resources  checked.
Don't crash when changing from "Switch betwen views with tabs" to "Merge all calendars into one view" when there aren't any resources 
checked.

svn path=/trunk/KDE/kdepim/; revision=956360

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