Do not set the content description on the icon tab when not necessary

It is not necessary to set the content description of a tab's icon
when the icon is not actually visible. Based on the implementation,
the tab's icon is only visible when not null and its visibility is
set to true.

Change-Id: I4430dfc7d1faa0ae00fdc789745e7cae7b453a89
Derp
Signed-off-by: franco-c <tjrdnjs33936@gmail.com>