client: Application.MainWindow: Always log error in the background

convo.get_count() will not be zero when an email is loaded while being
removed.

src/client/application/application-main-window.vala

@@ -1620,20 +1620,13 @@ public class Application.MainWindow :
                         );
                     } catch (Geary.EngineError.NOT_FOUND err) {
                         // The first interesting email from the
-                        // conversation wasn't found. If the
-                        // conversation has completely evaporated by
-                        // now then fine, otherwise throw the
-                        // error. This happens e.g. in the drafts
-                        // folder, there is a race between the
+                        // conversation wasn't found.
+                        // This happens:
+                        // - in the drafts folder, there is a race between the
                         // composer being discarded and the draft
                         // itself disappearing
-                        if (convo.get_count() == 0) {
-                            debug("Ignoring not found error: %s", err.message);
-                        } else {
-                            handle_error(
-                                convo.base_folder.account.information, err
-                            );
-                        }
+                        // - when message has been removed while being loaded
+                        debug("Ignoring not found error: %s", err.message);
                     } catch (GLib.IOError.CANCELLED err) {
                         // All good
                     } catch (GLib.Error err) {

src/engine/imap-db/imap-db-folder.vala

@@ -2616,3 +2616,4 @@ private class Geary.ImapDB.Folder : BaseObject, Geary.ReferenceSemantics {
     }
 
 }
+