dc_receive_imf: remove dead code

mimeparser ensures that mails have at least one part.

Besides that, add_parts() handles the case of no parts just fine.

src/dc_receive_imf.rs

@@ -164,7 +164,6 @@ pub(crate) async fn dc_receive_imf_inner(
     );
 
     // Add parts
-    if mime_parser.parts.last().is_some() {
     add_parts(
         context,
         &mut mime_parser,
@@ -189,13 +188,6 @@ pub(crate) async fn dc_receive_imf_inner(
     )
     .await
     .map_err(|err| err.context("add_parts error"))?;
-    } else {
-        // there are parts in this message, do some basic calculations so that the variables
-        // are correct in the further processing
-        if sent_timestamp > time() {
-            sent_timestamp = time()
-        }
-    }
 
     if mime_parser.location_kml.is_some() || mime_parser.message_kml.is_some() {
         save_locations(