Fix unsafe type assertion panic in metrics.go when status["total_size"] is nil

Co-authored-by: kira1928 <2352900+kira1928@users.noreply.github.com>
Agent-Logs-Url: https://github.com/bililive-go/bililive-go/sessions/e3b4acf7-a4ea-47c7-98c9-c51ca1cc43ee

src/metrics/metrics.go

@@ -80,9 +80,11 @@ func (c collector) Collect(ch chan<- prometheus.Metric) {
 
 				if r, err := c.inst.RecorderManager.(recorders.Manager).GetRecorder(context.Background(), id); err == nil {
 					if status, err := r.GetStatus(); err == nil {
-						if value, err := strconv.ParseFloat(status["total_size"].(string), 64); err == nil {
-							ch <- prometheus.MustNewConstMetric(recorderTotalBytes, prometheus.CounterValue, value,
-								string(id), l.GetRawUrl(), info.HostName, info.RoomName)
+						if totalSize, ok := status["total_size"].(string); ok {
+							if value, err := strconv.ParseFloat(totalSize, 64); err == nil {
+								ch <- prometheus.MustNewConstMetric(recorderTotalBytes, prometheus.CounterValue, value,
+									string(id), l.GetRawUrl(), info.HostName, info.RoomName)
+							}
 						}
 					}
 				}