The bottom layer cannot hold a valid spawn point
The bottom layer cannot hold a valid spawn point

Fixes #2510

Frownigami1/cuberite,kevinr/cuberite,SamOatesPlugins/cuberite,HelenaKitty/EbooMC,johnsoch/cuberite,johnsoch/cuberite,marvinkopf/cuberite,marvinkopf/cuberite,ionux/MCServer,nounoursheureux/MCServer,mc-server/MCServer,QUSpilPrgm/cuberite,Fighter19/cuberite,birkett/cuberite,QUSpilPrgm/cuberite,Haxi52/cuberite,Altenius/cuberite,birkett/MCServer,Fighter19/cuberite,Schwertspize/cuberite,QUSpilPrgm/cuberite,tonibm19/cuberite,Fighter19/cuberite,Frownigami1/cuberite,Haxi52/cuberite,kevinr/cuberite,birkett/MCServer,ionux/MCServer,mc-server/MCServer,Fighter19/cuberite,nounoursheureux/MCServer,ionux/MCServer,Schwertspize/cuberite,bendl/cuberite,johnsoch/cuberite,QUSpilPrgm/cuberite,tonibm19/cuberite,HelenaKitty/EbooMC,marvinkopf/cuberite,birkett/cuberite,mc-server/MCServer,SamOatesPlugins/cuberite,Fighter19/cuberite,tonibm19/cuberite,HelenaKitty/EbooMC,ionux/MCServer,Haxi52/cuberite,birkett/cuberite,bendl/cuberite,birkett/MCServer,QUSpilPrgm/cuberite,kevinr/cuberite,Frownigami1/cuberite,HelenaKitty/EbooMC,johnsoch/cuberite,marvinkopf/cuberite,mc-server/MCServer,HelenaKitty/EbooMC,Frownigami1/cuberite,Haxi52/cuberite,birkett/MCServer,Fighter19/cuberite,SamOatesPlugins/cuberite,kevinr/cuberite,tonibm19/cuberite,mc-server/MCServer,nounoursheureux/MCServer,kevinr/cuberite,Haxi52/cuberite,Altenius/cuberite,marvinkopf/cuberite,Altenius/cuberite,nounoursheureux/MCServer,birkett/MCServer,Altenius/cuberite,birkett/cuberite,birkett/cuberite,SamOatesPlugins/cuberite,bendl/cuberite,Frownigami1/cuberite,kevinr/cuberite,Schwertspize/cuberite,tonibm19/cuberite,SamOatesPlugins/cuberite,birkett/cuberite,mc-server/MCServer,bendl/cuberite,Altenius/cuberite,birkett/MCServer,tonibm19/cuberite,johnsoch/cuberite,ionux/MCServer,QUSpilPrgm/cuberite,nounoursheureux/MCServer,bendl/cuberite,Schwertspize/cuberite,nounoursheureux/MCServer,Schwertspize/cuberite,marvinkopf/cuberite,Haxi52/cuberite,ionux/MCServer