merge SVN commit 1102400 by winterz:

fix a crash when deleting a folder in the following test case:

1. Create a subfolder x2 of x1.
2. Copy all mails form x1 to x2.
3. Sync and while syncing delete folder x1

svn path=/tags/kdepim/enterprise35.0.20100305.1099257/kdepim/; revision=1102403