Add test for missing value in alternatives
Add test for missing value in alternatives

Related to #527.

bananaoomarang/joi,geminiyellow/joi,thethanghn/react-native-joi,jagoda/joi,danielb2/joi,pandeysoni/joi,lloydbenson/joi,davidbenko9/joi,rmoorman/joi,ck-lee/joi,pikselpalette/joi,olistic/joi-extended,tpiecora/joi,cesarmarinhorj/joi,jeffbski/joi,opyate/joi,robertherber/joi-extended,naitsric/joi