Make "hydra:mapping" item's property nullable (#3877)
Make "hydra:mapping" item's property nullable (#3877)


meyerbaptiste/core,api-platform/core,meyerbaptiste/core,api-platform/core,soyuka/core,meyerbaptiste/core,vincentchalamon/core,vincentchalamon/core,soyuka/core,soyuka/core,meyerbaptiste/core,soyuka/core,vincentchalamon/core,api-platform/core,api-platform/core,vincentchalamon/core