Delete all nodes of deque buffer

Author: Cuda-Chen

virtio-snd.c

@@ -644,9 +644,11 @@ static void virtio_snd_read_pcm_release(const virtio_snd_pcm_hdr_t *query,
     /* Tear down the PCM buffer queue */
     vsnd_buf_queue_node_t *tmp = NULL;
     vsnd_buf_queue_node_t *node;
-    list_for_each_entry_safe (node, tmp, &props->buf_queue_head, q) {
-        list_del(&node->q);
-        free(node);
+    if (!list_empty(&props->buf_queue_head)) {
+        list_for_each_entry_safe (node, tmp, &props->buf_queue_head, q) {
+            list_del(&node->q);
+            free(node);
+        }
     }
 
     CNFAClose(props->audio_host);