docs navigation icon and table of contens unvisible

TEST ENV:  chrome 70.0.3538.110 (Official Build) (64-bit)

                  firefox 64.0.2 (32-bit)

                  IE 11

                  Edge 41.16299.1004.0

Process:  for example,  open url below with default font size, http://docs.automotivelinux.org/master/docs/devguides/en/dev/reference/meta-agl-devel.html

the page's navi icon and table of contents can not be seen.

Only reset page font size to 200% plus,  they will appear.