Object Reference error - Order Post

[ {
"cancel_date" : null,
"ship_to" : null,
"cash_flag" : "N",
"freight" : 0,
"organization_id" : "SUSA",
"user_priority" : "",
"rate_type_home" : "BUY",
"so_priority_code" : "1",
"sold_to_city" : null,
"tax_perc" : 0,
"gross_sales" : 0,
"total_discount" : 0,
"void_who" : null,
"hold_reason" : null,
"ship_to_country" : "US",
"attention" : "Accounts Payable",
"cust_po" : null,
"dest_zone_code" : null,
"internal_so_ind" : 0,
"tax_valid_ind" : 0,
"route_code" : "",
"invoice_date" : null,
"addr_valid_ind" : 0,
"process_ctrl_num" : "",
"routing" : "BESTWAY",
"label_no" : 0,
"curr_key" : "USD",
"total_invoice" : 0.00,
"load_no" : 0,
"consolidate_flag" : 0,
"bill_to_key" : "CS011891",
"tot_ord_tax" : 0.84,
"req_ship_date" : "/Date(1415836800000+0000)/",
"sch_ship_date" : "/Date(1415836800000+0000)/",
"ship_to_name" : "Stony Tire",
"last_picked_dt" : null,
"sopick_ctrl_num" : null,
"route_no" : 0,
"status" : "N",
"forwarder_key" : "",
"orig_ext" : 0,
"freight_allow_pct" : 0,
"remit_key" : "LOCKBOX",
"ship_to_region" : "1006",
"tot_tax_incl" : 0,
"f_note" : "",
"total_amt_order" : 13.00,
"sold_to_addr1" : "",
"tot_ord_disc" : 0.00,
"changed" : "N",
"ext" : 0,
"type" : "I",
"terms" : "NET30",
"location" : "ZNRE",
"sold_to_country_cd" : "US",
"phone" : "7084744114",
"oper_factor" : 1.00,
"curr_factor" : 1.00,
"back_ord_flag" : "1",
"orderdetail" : [ {
"cr_ordered" : 0,
"unpicked_dt" : null,
"lb_tracking" : "N",
"direct_dolrs" : 0.00,
"return_code" : null,
"create_po_flag" : 0,
"weight_ea" : 0.00,
"back_ord_flag" : "1",
"printed" : null,
"ordered" : 2.00,
"organization_id" : "SUSA",
"tax_code" : "AVATAX",
"labor" : 0,
"reference_code" : "",
"util_dolrs" : 0.00,
"cubic_feet" : 0.00,
"std_direct_dolrs" : 0.00,
"line_no" : 3,
"picked_dt" : null,
"temp_price" : 0.00,
"void_who" : null,
"order_ext" : 0,
"note" : "Make:___________________________Model:______________________________ Lift#:___________________ S/N:_____________________ Hrs:________________ Customer's responsibility to check lug nuts 8 hours after service.",
"who_picked_id" : null,
"cust_po" : "",
"total_tax" : 0.00,
"agreement_id" : null,
"conv_factor" : 1,
"std_cost" : null,
"shipped" : 0,
"uom" : "EA",
"disc_code" : null,
"std_ovhd_dolrs" : 0.00,
"who_entered" : "asotomay",
"sales_comm" : 0,
"part_no" : "LIFT",
"qc_flag" : "N",
"price" : 0.00,
"curr_price" : 0.00,
"price_type" : "X",
"who_unpicked_id" : null,
"discount" : 0.00,
"cost" : 0.00,
"inv_available_flag" : "T",
"part_type" : "V",
"taxable" : 0,
"contract" : null,
"status" : "N",
"void_date" : null,
"reason_code" : null,
"service_agreement_flag" : "N",
"load_group_no" : 0,
"cr_shipped" : 0,
"description" : "LIFT INFORMATION",
"order_no" : 1521679,
"orig_part_no" : null,
"gl_rev_acct" : "42000100690990",
"oper_price" : 0.00,
"ovhd_dolrs" : 0.00,
"std_util_dolrs" : 0.00,
"printed_dt" : null,
"location" : "ZNRE",
"row_id" : null
}, {
"cr_ordered" : 0,
"unpicked_dt" : null,
"lb_tracking" : "Y",
"direct_dolrs" : 0.00,
"return_code" : null,
"create_po_flag" : 0,
"weight_ea" : 0.85,
"back_ord_flag" : "1",
"printed" : "N",
"ordered" : 1.00,
"organization_id" : "SUSA",
"tax_code" : "AVATAX",
"labor" : 0,
"reference_code" : "",
"util_dolrs" : 0.00,
"cubic_feet" : 0.11,
"std_direct_dolrs" : 0.00,
"line_no" : 1,
"picked_dt" : null,
"temp_price" : 13.00,
"void_who" : null,
"order_ext" : 0,
"note" : null,
"who_picked_id" : null,
"cust_po" : "",
"total_tax" : 0.84,
"agreement_id" : null,
"conv_factor" : 1,
"std_cost" : null,
"shipped" : 0,
"uom" : "EA",
"disc_code" : null,
"std_ovhd_dolrs" : 0.00,
"who_entered" : "asotomay",
"sales_comm" : 0,
"part_no" : "PIN10",
"qc_flag" : "N",
"price" : 13.00,
"curr_price" : 13.44,
"price_type" : "X",
"who_unpicked_id" : null,
"discount" : 0.00,
"cost" : 0.00,
"inv_available_flag" : "T",
"part_type" : "P",
"taxable" : 1,
"contract" : null,
"status" : "N",
"void_date" : null,
"reason_code" : null,
"service_agreement_flag" : "N",
"load_group_no" : 0,
"cr_shipped" : 0,
"description" : "10 X 16.5 PIN 10 X 16.5 SS SHAFT",
"order_no" : 1521679,
"orig_part_no" : "PIN10",
"gl_rev_acct" : "41320100620990",
"oper_price" : 0.00,
"ovhd_dolrs" : 0.00,
"std_util_dolrs" : 0.00,
"printed_dt" : null,
"location" : "ZNRE",
"row_id" : 3407078
} ],
"printed" : "N",
"ship_to_city" : "Lynwood",
"multiple_flag" : "N",
"fob" : "ORIGIN",
"user_category" : null,
"rate_type_oper" : "BUY",
"curr_type" : "0",
"orig_no" : 0,
"blanket_amt" : 0,
"void" : "N",
"sold_to_zip" : null,
"fo_order_no" : null,
"note" : null,
"eprocurement_ind" : 0,
"ship_to_add_2" : "Lynwood, Illinois, 60411-8671",
"total_tax" : 0,
"ship_to_add_1" : "19870 Stoney Island",
"tax_id" : "AVATAX",
"posting_code" : "3RDZNRE",
"blanket" : "N",
"freight_allow_type" : null,
"cust_code" : "CS011891",
"date_printed" : null,
"who_entered" : "asotomay",
"user_def_fld10" : 0,
"sales_comm" : 0,
"invoice_no" : 0,
"user_def_fld7" : 0,
"discount" : 0.00,
"user_def_fld6" : 0,
"user_def_fld5" : 0,
"user_def_fld4" : null,
"user_def_fld3" : "ZNRE",
"user_def_fld2" : null,
"user_def_fld1" : null,
"tot_ord_incl" : 0,
"freight_to" : null,
"void_date" : null,
"user_def_fld11" : 0,
"user_def_fld9" : null,
"user_def_fld12" : 0,
"user_def_fld8" : 0,
"salesperson" : "BATCHA",
"ship_to_country_cd" : "US",
"sold_to_state" : "IL",
"ship_to_state" : "IL",
"order_no" : 1521679,
"special_instr" : null,
"user_code" : "OPEN",
"invoice_edi" : "N",
"batch_code" : "",
"sold_to" : "",
"tot_ord_freight" : 0.00,
"ship_to_zip" : "60411-8671"
} ]