Check for empty expedition via database not cache

Checking the cache on member removal here isn't reliable due to race
with cross zone message

If a zone removes a member at the same time as another zone, neither zone
can know if the expedition will be empty via cache unless it processes the
world message from the other zone's member removal first.

zone/expedition.cpp

@@ -509,9 +509,13 @@ bool Expedition::RemoveMember(const std::string& remove_char_name)
 		ChooseNewLeader();
 	}
 
-	if (m_members.empty())
+	// we can't check for empty member count via cache because if other zones
+	// remove members at the same time then we race. cache member count won't
+	// be accurate until the world messages from other zones are processed
+	uint32_t member_count = ExpeditionDatabase::GetExpeditionMemberCount(m_id);
+	if (member_count == 0)
 	{
-		// cache removal will occur in world message handler
+		// zone cache removal will occur in world message handler
 		ExpeditionDatabase::DeleteExpedition(m_id);
 		if (RuleB(Expedition, EmptyDzShutdownEnabled))
 		{
@@ -1163,6 +1167,11 @@ void Expedition::ProcessMemberRemoved(std::string removed_char_name, uint32_t re
 
 		it = is_removed ? m_members.erase(it) : it + 1;
 	}
+
+	LogExpeditionsDetail(
+		"Processed member [{}] ({}) removal, current zone cache member count: [{}]",
+		removed_char_name, removed_char_id, m_members.size()
+	);
 }
 
 void Expedition::ProcessLockoutUpdate(
@@ -1581,6 +1590,11 @@ void Expedition::HandleWorldMessage(ServerPacket* pack)
 		auto expedition = Expedition::FindCachedExpeditionByID(buf->expedition_id);
 		if (expedition && zone)
 		{
+			LogExpeditionsDetail(
+				"World member change message -- remove: [{}] name: [{}] zone: [{}]:[{}] sender: [{}]:[{}]",
+				buf->removed, buf->char_name, zone->GetZoneID(), zone->GetInstanceID(), buf->sender_zone_id, buf->sender_instance_id
+			);
+
 			if (!zone->IsZone(buf->sender_zone_id, buf->sender_instance_id))
 			{
 				if (buf->removed)