save contentype

Author: Trolldemorted

Signal-Windows.Lib/IncomingMessages.cs

@@ -437,7 +437,7 @@ private void HandleSignalMessage(SignalServiceEnvelope envelope, SignalServiceCo
                         Message = message,
                         Status = (uint)SignalAttachmentStatus.Default,
                         SentFileName = pointer.FileName,
-                        ContentType = "",
+                        ContentType = receivedAttachment.getContentType(),
                         Key = pointer.Key,
                         Relay = pointer.Relay,
                         StorageId = pointer.Id,