Simplify the whole wait_for_marker commit.
Simplify the whole wait_for_marker commit.

Companion commit to the same stuff in base ;).

chrox/koreader,Frenzie/koreader,mihailim/koreader,ashhher3/koreader,apletnev/koreader,ashang/koreader,pazos/koreader,Hzj-jie/koreader,noname007/koreader,mwoz123/koreader,chihyang/koreader,Frenzie/koreader,koreader/koreader,koreader/koreader,frankyifei/koreader,poire-z/koreader,poire-z/koreader,lgeek/koreader,Markismus/koreader,robert00s/koreader,NiLuJe/koreader,NickSavage/koreader,houqp/koreader,NiLuJe/koreader