Error exporting uses when working with user custom fields, different instances, and setting the portal property "users.export.csv.fields"

Suppose that you have several Instances in a Liferay environment and add a custom field to the user object only in one of these instances. If you add this new custom field to the portal property "users.export.csv.fields" to add this one in the list of the attributes exported, the Instances that do not have this custom field fail when a users export is done.

The steps to reproduce the case are:

1. Create an Instance called IntanceA.

2. Create a user in the InstanceA.

3. Create an Instance called IntanceB.

4. Create a user in the InstanceB.

5. Create a user custom field in the InstanceA called custom1.

6. Add the property "users.export.csv.fields" to the portal-ext.properties with the value "users.export.csv.fields=fullName,emailAddress,expando:custom1".

7. Restart Liferay.

8. Go to InstanteB and try to export the users.

Expected result :

The export is done, and the custom1 column is empty. It must be empty because it does not exist in InstanceB.

Actual result :

An error happens, and the interface goes block. In the log file, the following error trace is registered.

Log output: