Forking issue with 0.4.1: uniqueness constraint is violated

[abitmore]

It's reported that 0.4.0 nodes are rejecting certain blocks produced by 0.4.1 node. Logs are here:

3480470ms th_a       steem_evaluator.cpp:569       do_apply             ] 10 assert_exception: Assert Exception
insert_result.second: Could not create object! Most likely a uniqueness constraint is violated.
    {}
    th_a  generic_index.hpp:63 create
3480470ms th_a       steem_evaluator.cpp:569       do_apply             ] o: {"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}
3480470ms th_a       database.cpp:1930             _apply_block         ] 10 assert_exception: Assert Exception
insert_result.second: Could not create object! Most likely a uniqueness constraint is violated.
    {}
    th_a  generic_index.hpp:63 create
rethrow
    {"o":{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}}
    th_a  steem_evaluator.cpp:569 do_apply

    {}
    th_a  evaluator.cpp:18 start_evaluate

    {}
    th_a  database.cpp:2075 apply_operation

    {"op":["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]}
    th_a  database.cpp:2056 _apply_transaction

    {"trx":{"ref_block_num":10724,"ref_block_prefix":3414704619,"expiration":"2016-05-10T08:58:06","operations":[["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]],"extensions":[],"signatures":[1f53abd8989022e6cceeb6690e41defdb5fbb3e5bcfec19992c0e32b3df6294aac2004f04fb2f799c9aa38579d89f16f3fe3fdea2aa934d6e73ca1aa5a5e2b2790"]}}
    th_a  database.cpp:2060 _apply_transaction
3480471ms th_a       database.cpp:558              _push_block          ] Failed to push new block:
10 assert_exception: Assert Exception
insert_result.second: Could not create object! Most likely a uniqueness constraint is violated.
    {}
    th_a  generic_index.hpp:63 create
rethrow
    {"o":{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}}
    th_a  steem_evaluator.cpp:569 do_apply

    {}
    th_a  evaluator.cpp:18 start_evaluate

    {}
    th_a  database.cpp:2075 apply_operation

    {"op":["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]}
    th_a  database.cpp:2056 _apply_transaction

    {"trx":{"ref_block_num":10724,"ref_block_prefix":3414704619,"expiration":"2016-05-10T08:58:06","operations":[["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]],"extensions":[],"signatures":["1f53abd8989022e6cceeb6690e41defdb5fbb3e5bcfec19992c0e32b3df6294aac2004f04fb2f799c9aa38579d89f16f3fe3fdea2aa934d6e73ca1aa5a5e2b2790"]}}
    th_a  database.cpp:2060 _apply_transaction
rethrow
    {}
    th_a  database.cpp:1930 _apply_block
3480471ms th_a       application.cpp:446           handle_block         ] Error when pushing block:
10 assert_exception: Assert Exception
insert_result.second: Could not create object! Most likely a uniqueness constraint is violated.
    {}
    th_a  generic_index.hpp:63 create
rethrow
    {"o":{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}}
    th_a  steem_evaluator.cpp:569 do_apply

    {}
    th_a  evaluator.cpp:18 start_evaluate

    {}
    th_a  database.cpp:2075 apply_operation

    {"op":["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]}
    th_a  database.cpp:2056 _apply_transaction

    {"trx":{"ref_block_num":10724,"ref_block_prefix":3414704619,"expiration":"2016-05-10T08:58:06","operations":[["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]],"extensions":[],"signatures":["1f53abd8989022e6cceeb6690e41defdb5fbb3e5bcfec19992c0e32b3df6294aac2004f04fb2f799c9aa38579d89f16f3fe3fdea2aa934d6e73ca1aa5a5e2b2790"]}}
    th_a  database.cpp:2060 _apply_transaction
rethrow
    {}
    th_a  database.cpp:1930 _apply_block

    {"new_block":{"previous":"001429e6d124925975b23c21c40d4150d37c45a2","timestamp":"2016-05-10T08:58:00","witness":"bitcube","transaction_merkle_root":"f7d0f8066a4615068e4e2e88be07d21b5ec59032","extensions":[],"witness_signature":"1f10ec56a5e53cfbf7d289c2931d7e151c4a1d1e9f4d4c97be55d9a424ece877076a67a180708b4ea80bf1783039798125e1b493d1926a42f1d2273891236230c4","transactions":[{"ref_block_num":10724,"ref_block_prefix":3414704619,"expiration":"2016-05-10T08:58:06","operations":[["vote",{"voter":"liondani","author":"liondani","permlink":"steem-a-blockchain-based-social-media-platform","weight":10000}]],"extensions":[],"signatures":["1f53abd8989022e6cceeb6690e41defdb5fbb3e5bcfec19992c0e32b3df6294aac2004f04fb2f799c9aa38579d89f16f3fe3fdea2aa934d6e73ca1aa5a5e2b2790"]}]}}
    th_a  database.cpp:564 _push_block

[abitmore]

In v0.4.1, when a comment is being edited, this code removes all votes for the comment. This behavior is different from which in v0.4.0.