[apiextensions] Remove nil check for map in PrepareForCreate
[apiextensions] Remove nil check for map in PrepareForCreate

Signed-off-by: Gaurav Singh <gaurav1086@gmail.com>

Kubernetes-commit: c96446ac2fed8f91a450c7e7704ac813497c1d01

kubernetes/apiextensions-apiserver,kubernetes/apiextensions-apiserver