Don't crash when dumpDeadLetters is called before we have a main window.
Don't crash when dumpDeadLetters is called before we have a main window.

CCMAIL: 59297-done@bugs.kde.org

svn path=/trunk/kdepim/; revision=229653

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