[netdev] Add a non-null judgment to the netstat command.|为 netstat 命令添加非空判断。

components/net/netdev/src/netdev.c

@@ -1159,8 +1159,15 @@ static void netdev_cmd_netstat(void)
         }
     }
 
+    if (netdev->ops->netstat != RT_NULL)
+    {
         netdev->ops->netstat(netdev);
     }
+    else
+    {
+        rt_kprintf("netstat: this command is not supported!\n");
+    }
+}
 
 int netdev_netstat(int argc, char **argv)
 {