Fix ipadb_multires resource handling
    
    * ipadb_get_pwd_policy() initializes struct ipadb_multires *res to NULL.
    * ipadb_multires_free() supports NULL as no-op.
    * ipadb_multibase_search() consistently frees and NULLs
      struct ipadb_multires **res on error.
    
    See: https://pagure.io/freeipa/issue/7738
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>