Do not drop requests after receiving mac if sas is not complete

When during verification we are the first party to complete the
verification workflow and then receive a (correct) MAC from the other
party, we need to send out the Done message even if we have not received
the Done message from the other party ourselves and are thus still
"WaitingForDone".

Author: ftilde

crates/matrix-sdk-crypto/src/verification/machine.rs

@@ -471,6 +471,18 @@ impl VerificationMachine {
 
                             if s.is_done() {
                                 self.mark_sas_as_done(s, content).await?;
+                            } else {
+                                // Even if we are not done (yet), there might be content to send
+                                // out, e.g. in the case where we are done with our side of the
+                                // verification process, but the other side has not yet sent their
+                                // "done".
+                                if let Some(content) = content {
+                                    self.queue_up_content(
+                                        s.other_user_id(),
+                                        s.other_device_id(),
+                                        content,
+                                    );
+                                }
                             }
                         } else {
                             flow_id_mismatch();