mirror: fix crash if tailing slash is in path
mirror: fix crash if tailing slash is in path

if you have a tailing slash in diskRoot config variable this will cause a crash on adapter start with the following message
"uncaught exception: Cannot read property 'ts' of undefined"

This is because an off by one error here:
https://github.com/ioBroker/ioBroker.javascript/blob/master/lib/mirror.js#L505
-> i.e. the first letter of the id goes missing there, so this.diskList get's filled with wrong keys and causes this.diskList[id] to be undefined in sync later.

ioBroker/ioBroker.javascript,ioBroker/ioBroker.javascript,ioBroker/ioBroker.javascript