Что означает этот элемент вывода в результате вызова с blocktrail api?

Это результат обращения к blocktrail api. Речь идет о транзакции с хешем 6b1c57d98a557b5f578c02f6c386ef049df5890ebddd01d286bf345f47c5cecc.

{"raw":"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","hash":"6b1c57d98a557b5f578c02f6c386ef049df5890ebddd01d286bf345f47c5cecc","first_seen_at":"2016-05-11T14:13:03+0000","last_seen_at":"2016-05-11T14:13:03+0000","block_height":411307,"block_time":"2016-05-11T14:15:43+0000","block_hash":"0000000000000000054ba46707cc4c736f47439040992cf3edc484fbb1e5b180","confirmations":44132,"is_coinbase":false,"estimated_value":665970,"total_input_value":681400,"total_output_value":671400,"total_fee":10000,"estimated_change":5430,"estimated_change_address":"18KGUfU2BXUm1e1KtCCrmz1Mdum4rGNvWt","high_priority":false,"enough_fee":true,"contains_dust":false,"inputs":[{"index":0,"output_hash":"d688982a2e84bc5dae3ea7372e8cd74c7fa3c48653a2bd7d81b54cf4d32dfdc4","output_index":2,"value":681400,"sequence":4294967295,"address":null,"type":"multisig","multisig":"1of3","multisig_addresses":["1HhfcdD1hRaim17m5qLEwGgHY7PBTb1Dof","1FkQMTyqzD2BK5PsmWX13AeJAHz5NEw7gq","17VLRV4y7g15KNhCepYvgigHHvREzbEmRn"],"script_signature":"00473044022077396917627358151b3a95abde6407d617fc2bcf2f2056e9a9096a7fea896b4002205c11958bc0dc6de05ee0c9b1ceaef7635cafcde6653c21a1a8a8f37af5e92eee01"}],"outputs":[{"index":0,"value":5430,"address":"18KGUfU2BXUm1e1KtCCrmz1Mdum4rGNvWt","type":"pubkeyhash","multisig":null,"multisig_addresses":null,"script":"OP_DUP OP_HASH160 503d498cfa360ab247c08a9cf73dc5f7f1a0a4ee OP_EQUALVERIFY OP_CHECKSIG","script_hex":"76a914503d498cfa360ab247c08a9cf73dc5f7f1a0a4ee88ac","spent_hash":"e3a462396931aaba740a459e79058f9ed9d98a39937b1e1b5832119b6d9dab0c","spent_index":0},{"index":1,"value":0,"address":null,"type":"op_return","multisig":null,"multisig_addresses":null,"script":"OP_RETURN 04fdfb5609aecb84f9f8f11f87bb1b7f9049805d3c6bee01d2199e99","script_hex":"6a1c04fdfb5609aecb84f9f8f11f87bb1b7f9049805d3c6bee01d2199e99","spent_hash":null,"spent_index":0},{"index":2,"value":665970,"address":null,"type":"multisig","multisig":"1of3","multisig_addresses":["1HhfcdD1hRaim17m5qLEwGgHY7PBTb1Dof","1FkQMTyqzD2BK5PsmWX13AeJAHz5NEw7gq","17VLRV4y7g15KNhCepYvgigHHvREzbEmRn"],"script":"OP_1 02ae22e5d5b7efdcfac8c955c57d0c18fa40e196c023f1756a89d2d4cc01706188 031466e0f4b7ae4e5ddfe4608ba2955f3aa045f92a2d9ec036d39395e752d307a1 03e5c24ea5185f7c4165a20db9b785db320dd73637f5a05b0eeed52cb6eaccb12b OP_3 OP_CHECKMULTISIG","script_hex":"512102ae22e5d5b7efdcfac8c955c57d0c18fa40e196c023f1756a89d2d4cc0170618821031466e0f4b7ae4e5ddfe4608ba2955f3aa045f92a2d9ec036d39395e752d307a12103e5c24ea5185f7c4165a20db9b785db320dd73637f5a05b0eeed52cb6eaccb12b53ae","spent_hash":"f2fc9d4aa6c7b9de1312e80f4df744f637453b947fbf428da5dce8b3b997c741","spent_index":0}],"opt_in_rbf":false,"lock_time_timestamp":null,"lock_time_block_height":null,"size":311,"is_double_spend":false,"double_spend_in":[]}

В массиве "outputs" есть этот элемент:

{"index":1,"value":0,"address":null,"type":"op_return","multisig":null,"multisig_addresses":null,"script":"OP_RETURN 04fdfb5609aecb84f9f8f11f87bb1b7f9049805d3c6bee01d2199e99","script_hex":"6a1c04fdfb5609aecb84f9f8f11f87bb1b7f9049805d3c6bee01d2199e99","spent_hash":null,"spent_index":0}

Почему он имеет значение null для обоих полей «адрес» и «multisig_addresses»? Что означает «OP_RETURN» в поле «сценарий»?