inputError v JS vracia null

Mam formular, ktory v latte manualne vykreslujem. Je to velky formular, preto tu ani zdrojaky nevkladam. Ma niekolko submit buttonov, vsetko funguje OK, ale:

Za niektorych okolnosti pred ulozenim formular zobrazi modal window. Moj modal window generujem javascriptom. Jeho obsah nastavujem v property content, kde som vlozil formularove prvky:

{* Modal Window pre zruseniu projektu *}
        {ifset $form['btn_cancel']}
            {input 'btn_cancel'}
            <div id="cancelDialog"></div>
            <script>
                $(function () {
                    "use strict";

                    $(document).ready(function () {

                        var cancelDialog = $("#cancelDialog");
                        var cancelDialogShow = $("#cancelDialogShow");

                        cancelDialog.kendoDialog({
                            width: "400px",
                            title: {_project.form.dialog_title_cancel},
                            closable: false,
                            modal: true,
                            visible: false,
                            content: `
                        <div class="k-form">
                            {label 'reason_cancelled_id'}<br/>
                            {input 'reason_cancelled_id'}<br/>
                            <span id="err_reason_cancelled_id" class="form-error-message">{inputError 'reason_cancelled_id'}</span><br/>
                            {label 'reason_cancelled_desc'}<br/>
                            {input 'reason_cancelled_desc'}<br/>
                            <span id="reason_cancelled_desc" class="form-error-message">{inputError 'reason_cancelled_desc'}</span>
                        </div>`,
                            actions: [
                                { text: {_cp.close}},
                                {
                                    text: {_cp.cancel}, primary: true, action: function () {
                                    var reason = $("select[name=reason_cancelled_id]").val().trim();
                                    var canSubmit = true;
                                    if (!reason) {
                                        canSubmit = false;
                                        $('#err_reason_cancelled_id').text({_form.validator.required});
                                    } else {
                                        $('#err_reason_cancelled_id').text('');
                                    }

                                    if (canSubmit) {
                                        alert('sss');
                                    }
                                    return false;
                                }
                                }
                            ]
                        });

                        cancelDialogShow.click(function () {
                            cancelDialog.data("kendoDialog").open();

                        });
                    });


                });
            </script>
        {/ifset}

Problem je, ze na kazdom mieste, kde pouzijem {inputError …} a inputError neobsahuje ziadnu chybovu hlasku sa zobrazi null a nie prazdny retazec. Ako mozem docielit, aby sa tam to null nezobrazovalo?

Dakujem.

Editoval steelbull (20. 4. 2018 19:31)