Zabbix DashBoard Graph widget goes blank/no data/empty.
原因是：仪表盘右上角的时间段被更改了，改回正确的时间段，图形就会恢复。
the root cause is: the time period of Dashboard has been changed. after you change back (like “Last 1 hour”), the graph will return to normally.
【已解决】Zabbix仪表板（仪表盘）图形变成空白/无数据/无图形