add redundant check for Null in Node
add redundant check for Null in Node

Fighter777/snakeyaml,marcuskara/snakeyaml,youxinren/snakeyaml,ilantoren/snakeyaml,yskumar007/snakeyaml,mc-nekoneko/snakeyaml,yeison/snakeyaml,jeremypepper/snakeyaml,votinhthieugia/snakeyaml,yishenggudou/snakeyaml,virustotalop/snakeyaml,umeding/snakeyaml,thinkofdeath/snakeyaml,ldh0826/snakeyaml,joy32812/snakeyaml,mapiman/snakeyaml,SorinS/snakeyaml,Akkrite/snakeyaml,cuizhennan/snakeyaml,AssafMashiah/assafmashiah-yaml,nxbdi/snakeyaml,Mause/snakeyaml,RussellSpitzer/snakeyaml,UcasRichard/snakeyaml