call the contract, expecting to return an empty list or empty map, but actually returning an exception

[sigrlot]

When I call the built-in contract, the contract normally returns an empty list or map, but it gives an exception.

1、getRestrictingInfo，the account does not have restricting：
expect: request complete， {'Code': 0, 'Ret': [] }
actual: request exception， {'Code': 304005, 'Ret': 'Account is not found on restricting contract'}

2、proposalList，no proposal:
expect: request complete， {'Code': 0, 'Ret': [] }
actual: request exception，{'Code': 2, 'Ret': 'Object not found' }

3、withdrawDelegateReward, no delegate:
{'jsonrpc': '2.0', 'id': 2, 'error': {'code': 4, 'message': 'inner contract exec failed', 'data': {'code': 305001, 'message': 'Delegation info not found'}}}

[benbaley]

Designed so.