KSMServer::tryRestore: fix indexing of saved application entries
Inspection of entries in .config/ksmserverrc suggests that the session application entries are indexed starting from 1, while the code seems to assume that it starts from 0. This wrong assumption leads to restoring only N-1 windows, when N windows were supposed to be restored.
I have only tested this patch on top of the v5.93.0 tag (I cannot build latest master on my machine due to older dependencies).