VnStat和 statistics都无法显示图片

[yangqiceng]

vnstat是空的，
statistics提示：/usr/lib/lua/luci/dispatcher.lua:474: Failed to execute call dispatcher target for entry '/admin/statistics/graph/cpu'.
The called action terminated with an exception:
/usr/lib/lua/luci/util.lua:200: attempt to get length of local 'str' (a nil value)
stack traceback:
[C]: in function 'assert'
/usr/lib/lua/luci/dispatcher.lua:474: in function 'dispatch'
/usr/lib/lua/luci/dispatcher.lua:126: in function </usr/lib/lua/luci/dispatcher.lua:125>