fixed crash at bottom of map
fixed crash at bottom of map

The pointers for spawn detection inside transparent blocks could be
invalid at the bottom layer of the map. Now all sections have an
additional check.

mrkite/minutor,EtlamGit/minutor,mrkite/minutor,Metibor/minutor,mrkite/minutor,EtlamGit/minutor,Metibor/minutor,mrkite/minutor,Metibor/minutor,Metibor/minutor,EtlamGit/minutor,EtlamGit/minutor,Metibor/minutor,EtlamGit/minutor,mrkite/minutor