[geary] engine: If email not found in outbox, do not queue it again. Prevent an infinite loop. Fix #781

[Cédric Bellegarde <cbellegarde src gnome org>]

commit 253795b5d4f73844531473b72539d9aabf9f9201
Author: Cédric Bellegarde <cedric.bellegarde@ædishatz.org>
Date:   Thu Aug 18 17:42:16 2022 +0200

    engine: If email not found in outbox, do not queue it again. Prevent an infinite loop. Fix #781

 src/engine/smtp/smtp-client-service.vala | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/engine/smtp/smtp-client-service.vala b/src/engine/smtp/smtp-client-service.vala
index 49c09cfa1..57c32890f 100644
--- a/src/engine/smtp/smtp-client-service.vala
+++ b/src/engine/smtp/smtp-client-service.vala
@@ -197,6 +197,7 @@ public class Geary.Smtp.ClientService : Geary.ClientService {
             } catch (GLib.IOError.CANCELLED err) {
                 // Nothing to do here — we're already cancelled.
             } catch (EngineError.NOT_FOUND err) {
+                email_handled = true;
                 debug("Queued email %s not found in outbox, ignoring: %s",
                       id.to_string(), err.message);
             } catch (GLib.Error err) {