Fix mob deserialization errors in the client (#4743)

The problem was seen while using the mobf mod package.

The problem happens when the server serializes entity attachments.
Sometimes, such attachments no longer exist. The serialization code
skips those. However, the total number of attachments was serialized
earlier.  Therefore the client expects more than it gets, and logs a
serialization error.

src/content_sao.cpp

@@ -383,23 +383,30 @@ std::string LuaEntitySAO::getClientInitializationData(u16 protocol_version)
 		writeF1000(os, m_yaw);
 		writeS16(os, m_hp);
 
-		writeU8(os, 4 + m_bone_position.size() + m_attachment_child_ids.size()); // number of messages stuffed in here
-		os<<serializeLongString(getPropertyPacket()); // message 1
-		os<<serializeLongString(gob_cmd_update_armor_groups(m_armor_groups)); // 2
-		os<<serializeLongString(gob_cmd_update_animation(
+		std::ostringstream msg_os(std::ios::binary);
+		msg_os << serializeLongString(getPropertyPacket()); // message 1
+		msg_os << serializeLongString(gob_cmd_update_armor_groups(m_armor_groups)); // 2
+		msg_os << serializeLongString(gob_cmd_update_animation(
 			m_animation_range, m_animation_speed, m_animation_blend, m_animation_loop)); // 3
 		for (UNORDERED_MAP<std::string, core::vector2d<v3f> >::const_iterator
 				ii = m_bone_position.begin(); ii != m_bone_position.end(); ++ii) {
-			os << serializeLongString(gob_cmd_update_bone_position((*ii).first,
+			msg_os << serializeLongString(gob_cmd_update_bone_position((*ii).first,
 					(*ii).second.X, (*ii).second.Y)); // m_bone_position.size
 		}
-		os<<serializeLongString(gob_cmd_update_attachment(m_attachment_parent_id, m_attachment_bone, m_attachment_position, m_attachment_rotation)); // 4
+		msg_os << serializeLongString(gob_cmd_update_attachment(m_attachment_parent_id,
+			m_attachment_bone, m_attachment_position, m_attachment_rotation)); // 4
+		int message_count = 4 + m_bone_position.size();
 		for (UNORDERED_SET<int>::const_iterator ii = m_attachment_child_ids.begin();
 				(ii != m_attachment_child_ids.end()); ++ii) {
 			if (ServerActiveObject *obj = m_env->getActiveObject(*ii)) {
-				os << serializeLongString(gob_cmd_update_infant(*ii, obj->getSendType(), obj->getClientInitializationData(protocol_version)));
+				message_count++;
+				msg_os << serializeLongString(gob_cmd_update_infant(*ii, obj->getSendType(),
+					obj->getClientInitializationData(protocol_version)));
 			}
 		}
+
+		writeU8(os, message_count);
+		os.write(msg_os.str().c_str(), msg_os.str().size());
 	}
 	else
 	{
@@ -865,26 +872,35 @@ std::string PlayerSAO::getClientInitializationData(u16 protocol_version)
 		writeF1000(os, m_yaw);
 		writeS16(os, getHP());
 
-		writeU8(os, 6 + m_bone_position.size() + m_attachment_child_ids.size()); // number of messages stuffed in here
-		os<<serializeLongString(getPropertyPacket()); // message 1
-		os<<serializeLongString(gob_cmd_update_armor_groups(m_armor_groups)); // 2
-		os<<serializeLongString(gob_cmd_update_animation(
+		std::ostringstream msg_os(std::ios::binary);
+		msg_os << serializeLongString(getPropertyPacket()); // message 1
+		msg_os << serializeLongString(gob_cmd_update_armor_groups(m_armor_groups)); // 2
+		msg_os << serializeLongString(gob_cmd_update_animation(
 			m_animation_range, m_animation_speed, m_animation_blend, m_animation_loop)); // 3
 		for (UNORDERED_MAP<std::string, core::vector2d<v3f> >::const_iterator
 				ii = m_bone_position.begin(); ii != m_bone_position.end(); ++ii) {
-			os<<serializeLongString(gob_cmd_update_bone_position((*ii).first, (*ii).second.X, (*ii).second.Y)); // m_bone_position.size
+			msg_os << serializeLongString(gob_cmd_update_bone_position((*ii).first,
+				(*ii).second.X, (*ii).second.Y)); // m_bone_position.size
 		}
-		os<<serializeLongString(gob_cmd_update_attachment(m_attachment_parent_id, m_attachment_bone, m_attachment_position, m_attachment_rotation)); // 4
-		os<<serializeLongString(gob_cmd_update_physics_override(m_physics_override_speed,
+		msg_os << serializeLongString(gob_cmd_update_attachment(m_attachment_parent_id,
+			m_attachment_bone, m_attachment_position, m_attachment_rotation)); // 4
+		msg_os << serializeLongString(gob_cmd_update_physics_override(m_physics_override_speed,
 				m_physics_override_jump, m_physics_override_gravity, m_physics_override_sneak,
 				m_physics_override_sneak_glitch)); // 5
-		os << serializeLongString(gob_cmd_update_nametag_attributes(m_prop.nametag_color)); // 6 (GENERIC_CMD_UPDATE_NAMETAG_ATTRIBUTES) : Deprecated, for backwards compatibility only.
+		// (GENERIC_CMD_UPDATE_NAMETAG_ATTRIBUTES) : Deprecated, for backwards compatibility only.
+		msg_os << serializeLongString(gob_cmd_update_nametag_attributes(m_prop.nametag_color)); // 6
+		int message_count = 6 + m_bone_position.size();
 		for (UNORDERED_SET<int>::const_iterator ii = m_attachment_child_ids.begin();
 				ii != m_attachment_child_ids.end(); ++ii) {
 			if (ServerActiveObject *obj = m_env->getActiveObject(*ii)) {
-				os << serializeLongString(gob_cmd_update_infant(*ii, obj->getSendType(), obj->getClientInitializationData(protocol_version)));
+				message_count++;
+				msg_os << serializeLongString(gob_cmd_update_infant(*ii, obj->getSendType(),
+					obj->getClientInitializationData(protocol_version)));
 			}
 		}
+
+		writeU8(os, message_count);
+		os.write(msg_os.str().c_str(), msg_os.str().size());
 	}
 	else
 	{