ARIA role presentation conflicts with the empty alt

The markup <img role="presentation" alt="alt text"> is contradictory.

According to https://www.w3.org/TR/2017/WD-wai-aria-practices-1.1-20170628/examples/presentation/PresentationRoleExamples.html, it is recommended that authors instead use empty alt text (alt="") where they use role="presentation".

There are places such as blocks/recentlyaccesseditems/templates/no-items.mustache and course/templates/no-courses.mustache that are using 'role="presentation"' with non-empty alt.