[4.10.x] fix: API export CRD failure

[mergify]

This is an automatic copy of pull request #15788 done by Mergify.

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Issue

https://gravitee.atlassian.net/browse/APIM-12926

Description

Area	File	Change
Repository	JdbcUserRepository.java	In findByIds(Collection<String> ids), return Collections.emptySet() when ids is null or empty to avoid invalid SQL WHERE u.id IN ().
Service	UserCrudServiceImpl.java	In findBaseUsersByIds(List<String> userIds), return Set.of() when userIds is null or empty so the repository is not called with an empty list.
Export	ApiCRDExportDomainServiceImpl.java	In setMembersSourceId(), only set sourceId/source when a user is found (user != null) so group-only members without a user record do not cause NPE.

Screen.Recording.2026-03-18.at.10.20.59.PM.mov

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