[core] Fix group roaming message fetching

mirai-core/src/commonMain/kotlin/contact/roaming/RoamingMessagesImplGroup.kt

@@ -30,6 +30,7 @@ internal class RoamingMessagesImplGroup(
         filter: RoamingMessageFilter?
     ): Flow<MessageChain> {
         var currentSeq: Int = getLastMsgSeq() ?: return emptyFlow()
+        var lastOfferedSeq = -1
 
         return flow {
             while (true) {
@@ -52,10 +53,14 @@ internal class RoamingMessagesImplGroup(
 
                 val maxTime = messageTimeSequence.max()
 
-                if (maxTime < timeStart) break // we have fetched all messages
+
+                // we have fetched all messages
+                // note: maxTime = 0 means all fetched messages were recalled
+                if (maxTime < timeStart && maxTime != 0) break
 
                 emitAll(
                     resp.msgElem.asSequence()
+                        .filter { lastOfferedSeq == -1 || it.msgHead.msgSeq < lastOfferedSeq }
                         .filter { it.time in timeStart..timeEnd }
                         .sortedByDescending { it.msgHead.msgSeq } // Ensure caller receiver newer messages first
                         .filter { filter.apply(it) } // Call filter after sort
@@ -63,7 +68,8 @@ internal class RoamingMessagesImplGroup(
                         .map { listOf(it).toMessageChainOnline(bot, contact.id, MessageSourceKind.GROUP) }
                 )
 
-                currentSeq = resp.msgElem.minBy { it.time }.msgHead.msgSeq
+                currentSeq = resp.msgElem.first().msgHead.msgSeq
+                lastOfferedSeq = currentSeq
             }
         }
     }