fix: gap fill outliers that are missing prev events

Signed-off-by: Erwan Leboucher <erwanleboucher@gmail.com>

changelog.d/+gap-fill-outlier-missing-prevs.bugfix.md

@@ -0,0 +1 @@
+Fix gap filling skipping outlier events that are missing their previous events. Contributed by @eleboucher.

src/service/rooms/event_handler/fetch_and_handle_outliers.rs

@@ -310,9 +310,9 @@ impl super::Service {
 							.stream()
 							.fold(0_u8, |i, event_id| async move {
 								if self.services.timeline.pdu_exists(event_id).await {
-									i.expected_add(1)
-								} else {
 									i
+								} else {
+									i.expected_add(1)
 								}
 							})
 							.await;