fix for project not building due to changes in grails-data-mapping

[benrhine]

No description provided.

[ilopmar]

Removing the throws from the signature will break Glassfish/Payara support. @ddelponte, please, can you comment here?

[ilopmar]

Sorry but I'm wrong. @ddelponte fixed it in the parent class and you're doing it in the child class so everything should work.

Sorry for the noise.

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