[hotfix] Version: empty pattern max is an empty string, not nil! (#4299)
[hotfix] Version: empty pattern max is an empty string, not nil! (#4299)

Fixes #4298.
Frenzie/koreader,Hzj-jie/koreader,poire-z/koreader,NiLuJe/koreader,koreader/koreader,Markismus/koreader,NiLuJe/koreader,pazos/koreader,mihailim/koreader,mwoz123/koreader,houqp/koreader,koreader/koreader,Frenzie/koreader,poire-z/koreader