Fix Kolab issue #45, pt.1:

If we do KMMessage::fromDwString(), we get to the calls that set the various
state flags from header fields. If those header fields are not there, then
setMDNSentState( 0 ) will be called. But 0 isn't a value in the resp. enum.
Catch this case and make it set the mdn sent state to unkown instead.

svn path=/trunk/kdepim/; revision=330149

kmmessage.cpp

@@ -4158,6 +4158,8 @@ void KMMessage::setSignatureState(KMMsgSignatureState s, int idx)
 void KMMessage::setMDNSentState( KMMsgMDNSentState status, int idx ) {
   if ( mMDNSentState == status )
     return;
+  if ( status == 0 )
+    status = KMMsgMDNStateUnknown;
   mMDNSentState = status;
   mDirty = true;
   KMMsgBase::setMDNSentState( status, idx );