People Picker Control Using JavaScript no longer working

I have a few people picker controls on newform.aspx that seem to have stopped pre-populating. 

I get this error...

            input.value = currentUser;//'Default Specification Assignment';Unable to set property 'value' of undefined or null reference

<script type="text/javascript">
    _spBodyOnLoadFunctionNames.push("fillDefaultValues");
    function fillDefaultValues() {

        var userid = _spPageContextInfo.userId;


            $.ajax({
                url: _spPageContextInfo.webAbsoluteUrl + "/_api/web/getuserbyid(" + userid + ")",
                contentType: "application/json;odata=verbose",
                headers: { "accept": "application/json;odata=verbose" },
                success: onSuccess,
                error: onError
            });

        function onSuccess(data, request) {
            var currentUser = data.d.Title;

            var div, input, picker;

            div= getTagFromIdentifierAndTitle("div", "", "Specification Assignment");
            input = getTagFromIdentifierAndTitle("input", "", "Specification Assignment");
            input.value = currentUser;//'Default Specification Assignment Group';
            picker = SPClientPeoplePicker.SPClientPeoplePickerDict[div.id];
            picker.AddUnresolvedUserFromEditor(true);

        }
        function onError(error) {
            alert(error);
        }
    }

    function getTagFromIdentifierAndTitle(tagName, identifier, title) {
        var len = identifier.length;
        var tags = document.getElementsByTagName(tagName);
        for (var i = 0; i < tags.length; i++) {
            var tempString = tags[i].id;
            if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) {
                return tags[i];
            }
        }
        return null;
    }</script>

Thank you!