Fix getEventString()
Fix getEventString()

This code will no be executed, since all `MegaEvent` instances are
`MegaEventPrivate` objects, indeed. But it should be fixed anyway.

meganz/sdk,Acidburn0zzz/sdk,meganz/sdk,Acidburn0zzz/sdk,Acidburn0zzz/sdk,Acidburn0zzz/sdk,Acidburn0zzz/sdk,meganz/sdk,meganz/sdk,Acidburn0zzz/sdk,meganz/sdk,meganz/sdk,Acidburn0zzz/sdk,Acidburn0zzz/sdk,meganz/sdk