音量设置最小时，用以显示文本的数值异常

Log: 修改音量设置最小时文案异常问题
Bug: https://pms.uniontech.com/zentao/bug-view-47091.html
Change-Id: I44829a1e5a8e1180afa18dcb8d74996c7d114d03
Reviewed-on: http://gerrit.uniontech.com/c/dde-control-center/+/4199
Reviewed-by: niecheng <niecheng@uniontech.com>
Reviewed-by: wangwei <wangwei@uniontech.com>
Reviewed-by: <mailman@uniontech.com>
Tested-by: <mailman@uniontech.com>