Protocol 1.8: Added checks for values presence.
Protocol 1.8: Added checks for values presence.

Reported by @worktycho / Coverity.

tonibm19/cuberite,mmdk95/cuberite,mmdk95/cuberite,Tri125/MCServer,birkett/cuberite,tonibm19/cuberite,nichwall/cuberite,bendl/cuberite,jammet/MCServer,Howaner/MCServer,ionux/MCServer,nounoursheureux/MCServer,guijun/MCServer,mjssw/cuberite,marvinkopf/cuberite,jammet/MCServer,ionux/MCServer,Frownigami1/cuberite,electromatter/cuberite,Frownigami1/cuberite,Schwertspize/cuberite,marvinkopf/cuberite,linnemannr/MCServer,thetaeo/cuberite,nounoursheureux/MCServer,mc-server/MCServer,birkett/cuberite,mjssw/cuberite,nichwall/cuberite,guijun/MCServer,ionux/MCServer,marvinkopf/cuberite,nicodinh/cuberite,birkett/MCServer,nounoursheureux/MCServer,Schwertspize/cuberite,johnsoch/cuberite,Frownigami1/cuberite,linnemannr/MCServer,kevinr/cuberite,johnsoch/cuberite,nicodinh/cuberite,Howaner/MCServer,mmdk95/cuberite,mjssw/cuberite,mjssw/cuberite,tonibm19/cuberite,nicodinh/cuberite,birkett/cuberite,QUSpilPrgm/cuberite,nevercast/cuberite,QUSpilPrgm/cuberite,zackp30/cuberite,Schwertspize/cuberite,Howaner/MCServer,zackp30/cuberite,marvinkopf/cuberite,birkett/MCServer,Altenius/cuberite,guijun/MCServer,jammet/MCServer,birkett/MCServer,nevercast/cuberite,Tri125/MCServer,thetaeo/cuberite,SamOatesPlugins/cuberite,johnsoch/cuberite,Fighter19/cuberite,nicodinh/cuberite,kevinr/cuberite,birkett/MCServer,bendl/cuberite,birkett/cuberite,Altenius/cuberite,thetaeo/cuberite,nicodinh/cuberite,nevercast/cuberite,linnemannr/MCServer,Tri125/MCServer,Haxi52/cuberite,mmdk95/cuberite,SamOatesPlugins/cuberite,ionux/MCServer,tonibm19/cuberite,SamOatesPlugins/cuberite,nevercast/cuberite,Fighter19/cuberite,jammet/MCServer,kevinr/cuberite,zackp30/cuberite,nounoursheureux/MCServer,nevercast/cuberite,HelenaKitty/EbooMC,nicodinh/cuberite,SamOatesPlugins/cuberite,tonibm19/cuberite,Frownigami1/cuberite,Tri125/MCServer,johnsoch/cuberite,linnemannr/MCServer,Haxi52/cuberite,linnemannr/MCServer,ionux/MCServer,zackp30/cuberite,QUSpilPrgm/cuberite,thetaeo/cuberite,johnsoch/cuberite,QUSpilPrgm/cuberite,Tri125/MCServer,Frownigami1/cuberite,QUSpilPrgm/cuberite,kevinr/cuberite,electromatter/cuberite,Schwertspize/cuberite,tonibm19/cuberite,QUSpilPrgm/cuberite,bendl/cuberite,birkett/MCServer,Fighter19/cuberite,Haxi52/cuberite,linnemannr/MCServer,Howaner/MCServer,Howaner/MCServer,SamOatesPlugins/cuberite,birkett/MCServer,Altenius/cuberite,nichwall/cuberite,nevercast/cuberite,Howaner/MCServer,mc-server/MCServer,Altenius/cuberite,electromatter/cuberite,HelenaKitty/EbooMC,marvinkopf/cuberite,jammet/MCServer,HelenaKitty/EbooMC,birkett/cuberite,electromatter/cuberite,nichwall/cuberite,Haxi52/cuberite,mmdk95/cuberite,mmdk95/cuberite,mjssw/cuberite,thetaeo/cuberite,Fighter19/cuberite,mjssw/cuberite,guijun/MCServer,Fighter19/cuberite,Haxi52/cuberite,ionux/MCServer,nichwall/cuberite,HelenaKitty/EbooMC,Haxi52/cuberite,Fighter19/cuberite,kevinr/cuberite,nounoursheureux/MCServer,nounoursheureux/MCServer,bendl/cuberite,electromatter/cuberite,zackp30/cuberite,kevinr/cuberite,guijun/MCServer,mc-server/MCServer,electromatter/cuberite,mc-server/MCServer,Tri125/MCServer,Altenius/cuberite,zackp30/cuberite,birkett/cuberite,jammet/MCServer,thetaeo/cuberite,HelenaKitty/EbooMC,bendl/cuberite,Schwertspize/cuberite,mc-server/MCServer,nichwall/cuberite,marvinkopf/cuberite,guijun/MCServer,mc-server/MCServer