Fix nickel doesn't recognize sdcard after exiting
Fix nickel doesn't recognize sdcard after exiting

After exiting koreader, nickel will not recognize that sdcard is present.
This patch fixes that
ashhher3/koreader,noname007/koreader,poire-z/koreader,lgeek/koreader,NiLuJe/koreader,robert00s/koreader,pazos/koreader,apletnev/koreader,NiLuJe/koreader,mwoz123/koreader,Hzj-jie/koreader,mihailim/koreader,Frenzie/koreader,koreader/koreader,koreader/koreader,houqp/koreader,NickSavage/koreader,chrox/koreader,frankyifei/koreader,Markismus/koreader,Frenzie/koreader,chihyang/koreader,poire-z/koreader