ota(fix): do not create 0 size installed file if index is missing
ota(fix): do not create 0 size installed file if index is missing

NiLuJe/koreader,Hzj-jie/koreader,Frenzie/koreader,mihailim/koreader,NiLuJe/koreader,robert00s/koreader,Frenzie/koreader,poire-z/koreader,mwoz123/koreader,koreader/koreader,lgeek/koreader,poire-z/koreader,koreader/koreader,Markismus/koreader,pazos/koreader,apletnev/koreader,houqp/koreader