store: clean marked messages

Clean marked messages after new uids are fetched.

Commit 5c5158b3 ("store: remove callbacks on error") removed side
effects in the message store after a longer suspend period but neglected
to remove marked zombie messages.

References: https://todo.sr.ht/~rjarry/aerc/28
Co-authored-by: inwit <inwit@sindominio.net>
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

lib/msgstore.go

@@ -208,6 +208,7 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		store.Messages = newMap
 		store.uids = msg.Uids
 		sort.SortBy(store.filtered, store.uids)
+		store.checkMark()
 		update = true
 	case *types.DirectoryThreaded:
 		var uids []uint32
@@ -228,6 +229,7 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		}
 		store.Messages = newMap
 		store.uids = uids
+		store.checkMark()
 		store.Threads = msg.Threads
 		update = true
 	case *types.MessageInfo:
@@ -572,6 +574,22 @@ func (store *MessageStore) resetMark() {
 	store.marked = make(map[uint32]struct{})
 }
 
+// checkMark checks that no stale uids remain marked
+func (store *MessageStore) checkMark() {
+	for mark := range store.marked {
+		present := false
+		for _, uid := range store.uids {
+			if mark == uid {
+				present = true
+				break
+			}
+		}
+		if !present {
+			delete(store.marked, mark)
+		}
+	}
+}
+
 //IsMarked checks whether a MessageInfo has been marked
 func (store *MessageStore) IsMarked(uid uint32) bool {
 	_, marked := store.marked[uid]