Fix for new folder settings not saved (see PATCH mail on kmail-devel).

Patch semi-approved by Carsten and semi-approved by Till, which makes it fully approved.
If it saved mGuessedUnreadMsgs it would get into mUnreadMsgs on re-reading,
which would be wrong I guess. But when we have a guess, don't save mUnreadMsgs,
to be closer to the old behavior (we'll guess again on reopening, I suppose?).

svn path=/trunk/kdepim/; revision=303284

folderstorage.cpp

@@ -796,7 +796,7 @@ void FolderStorage::writeConfig()
 {
   KConfig* config = KMKernel::config();
   KConfigGroupSaver saver(config, "Folder-" + folder()->idString());
-  config->writeEntry("UnreadMsgs", countUnread());
+  config->writeEntry("UnreadMsgs", mGuessedUnreadMsgs == -1 ? mUnreadMsgs : -1);
   config->writeEntry("TotalMsgs", mTotalMsgs);
   config->writeEntry("Compactable", mCompactable);