Exception while patch of EnterpriseUser details

After using Apache Scimple in my SpringBoot application, I tried to test it via [scim2-tester](https://scim2-tester.readthedocs.io/en/latest/) but it failed in all patch operations of Enterprise user with below exception.

`ERROR check_replace_attribute
Failed to replace attribute 'urn:ietf:params:scim:schemas:extension:enterprise:2.0:User:costCenter': The server returned a SCIM Error object: Cannot invoke "java.util.Map.get(Object)" because "sourceAsMap" is null`

After analyzing, I checked that while create operation I persisted `org.apache.directory.scim.spec.resources.ScimUser` in database and all details got saved including enterprise User extension ones correctly but while deserializing the same into `org.apache.directory.scim.spec.resources.ScimUser` it does not read extensions attribute.

Please suggest.

Start by reproducing the Enterprise User patch failure with scim2-tester and trace deserialization of the persisted org.apache.directory.scim.spec.resources.ScimUser. Verify that the enterprise extension survives the database round trip and that replacing costCenter completes without the sourceAsMap exception.

Written by the indexing model from the issue text.