JsonUtils.replaceValue fails when given null value

[hauntingEcho]

Describe the bug When a function which calls JsonUtils.replaceValue is given a null, an NullPointerException is thrown by UpdatingNodeVisitor when attempting to deepCopy() that null.

To Reproduce construct a GenericScimResource x and call x.setSchemaUrns(null).

Expected behavior the Schemas element is removed from the resource

Additional context This can be necessary to construct a PATCH operation on an overall Group object, in which you don't want to edit the schema URNs.