use study chapter number as sort handle on mobile (closes #5631)
use study chapter number as sort handle on mobile (closes #5631)

arex1337/lila,luanlv/lila,luanlv/lila,luanlv/lila,arex1337/lila,arex1337/lila,luanlv/lila,luanlv/lila,luanlv/lila,arex1337/lila,arex1337/lila,arex1337/lila,arex1337/lila,luanlv/lila