[statistic plugin] Don't generate md5 sum on open document (#5528)
[statistic plugin] Don't generate md5 sum on open document (#5528)

There is no need to generate a md5 sum for documents that were already opened.
pazos/koreader,poire-z/koreader,Hzj-jie/koreader,koreader/koreader,Frenzie/koreader,NiLuJe/koreader,koreader/koreader,Markismus/koreader,mwoz123/koreader,mihailim/koreader,Frenzie/koreader,poire-z/koreader,NiLuJe/koreader