On Editor entry form, how do I allow a null input?

Code below. for min_amount and max_amount fields, I would like to be able to enter new data or edit data with the option of putting in a number or leaving the field blank or null value.

        {% include "dt_csrf.html" %}

        $('#opex').DataTable(
        );
        $('#otherexp').DataTable(
        );

        let bldg = {{ bldg.id}};
        console.log("bldg" + " " + bldg);

        let editor = new $.fn.dataTable.Editor({
            ajax: "/api/exptiedrev/editor/?format=datatables",
            table: "#exp",
            fields: [
                {
                    label: "Name",
                    name: "name"
                },
                {
                    label: "Type",
                    name: "exp_type",
                    type: "select",
                    options: [
                        {label: "Operating Expense", value: "Operating Expense"},
                        {label: "Other Expenses", value: "Other Expenses"}
                    ],
                    def: "Operating Expense"
                },
                {
                    label: "Revenue Type",
                    name: "rev_type",
                    type: "select",
                    options: [
                        {label: "Base Rent", value: "Base Rent"},
                        {label: "Gross Rent", value: "Gross Rent"}
                    ],
                    def: "Base Rent"
                },
                {
                    label: "Charge Rate %",
                    name: "charge_rate"
                },
                {
                    label: "Min, Charge $",
                    name: "min_amount"
                },
                {
                    label: "Maximum Charge $",
                    name: "max_aumount"
                },

            ],
        });

        editor.on('preSubmit', function (e, data, action) {
            if (action === 'create') {
                data.data[0]['bldg'] = parseInt(bldg);
            }
        });

        // Activate an inline edit on click of a table cell
        $('#exp').on('click', 'tbody td ', function (e) {
            editor.inline(this);
        });

        let table_rev_exp = $('#exp').DataTable({
            "serverSide": true,
            dom: "Bfrtip",
            "ajax": "/api/exptiedrev/?format=datatables&bldg=" + bldg,
            "columns": [
                {"data": "bldg"},
                {"data": "name"},
                {"data": "exp_type"},
                {"data": "rev_type"},
                {
                    "data": "charge_rate",
                    "render": function (data, type, row) {
                        return data + "%";
                    }
                },
                {"data": "min_amount", render: $.fn.dataTable.render.number(',', '.', 2, '$')},
                {"data": "max_amount", render: $.fn.dataTable.render.number(',', '.', 2, '$')},
            ],
            select: true,
            buttons: [
                {extend: "create", editor: editor},
                {extend: "edit", editor: editor},
                {extend: "remove", editor: editor},
                {
                    extend: 'collection',
                    text: 'Export',
                    buttons: [
                        {
                            extend: 'excelHtml5',
                            customize: function (xlsx) {
                                $(xlsx.xl["styles.xml"]).find('numFmt[numFmtId="164"]').attr('formatCode',
                                    '[$$-45C] #,##0.00_-');
                            },
                            exportOptions: {
                                columns: [1, 2, 3, 4, 5, 6],
                            },
                            title: "Expenses"

                        },
                        {
                            extend: 'pdfHtml5',
                            exportOptions: {
                                columns: [1, 2, 3, 4, 5, 6]
                            },
                            title: "Expenses"
                        },
                        {
                            extend: 'print',
                            exportOptions: {
                                columns: [1, 2, 3, 4, 5, 6]
                            },
                            title: " Expenses"
                        },
                    ]
                },
            ],
            "columnDefs": [
                {
                    "targets": [0],
                    "visible": false,
                    "searchable": false
                }
            ],
        });

        table_rev_exp.buttons().container()
            .appendTo($('.col-md-6:eq(0)', table_rev_exp.table().container()));

    });