编辑帖子上的错误在Ajax调用中显示422（不可处理的实体）

Question

我一直收到422（不可处理的实体）错误，我该如何解决这个问题？ 以下是关于ajax调用的代码，有人可以帮我解决这个问题吗？

    $(document).on('click', '.edit-post', function() {

        $('.edit-modal').css('display','block');
        $('.posts-table').css('display','none');


        var id = $(this).attr('data-id');
        var title = $(this).attr('data-title');
        var slug = $(this).attr('data-slug');
        var category = $(this).attr('data-category');
        var featured_image = $(this).attr('data-image');
        var body = $(this).attr('data-body');

        $('#edit-post-form #edit-title').val(title);
        $('#edit-post-form #edit-slug').val(slug);
        $('#edit-post-form #edit-category').val(category);
        //$('#edit-post-form #edit-image').val(featured_image);
        $('#edit-post-form #edit-body').val(body);
        $('#edit-id').val($(this).data('id'));


    });
    //Update New Post
    $("#update-post").click(function(e) {
        e.preventDefault();
        id = $('#edit-id').val();
        var title = $('#edit-post-form #edit-title').val();
        var slug = $('#edit-post-form #edit-slug').val();
        var category_id = $('#edit-post-form #edit-category').val();
        var featured_image = $('#edit-post-form #edit-image').val();
        var body = $('#edit-post-form #edit-body').val();

        var form = new FormData();
        form.append('title', title);
        form.append('slug', slug);
        form.append('category_id', category_id);
        form.append('featured_image', featured_image);
        form.append('body', body);


        $.ajax({
            type:'PUT',
            url: "/updatepost/" + id,
            headers: {
                'X-CSRF-TOKEN' : $('input[name="_token"]').val()
            },
            dataType: 'json',
            cache: false,
            contentType: false,
            processData: false,
            data: form,
            success: function(data) {
                    toastr.success('Successfully Updated Post!', 'Success Alert', {timeOut: 5000});
                    $('#'+ id).html("<tr id='" + data.id + "' class='item'><th>" + data.id + "</th><td>" + data.title + "</td><td>" + data.body + "</td><td>" + data.created_at + "</td><td><button class='edit-modal btn btn-info' data-id='" + data.id + "' data-title='" + data.title + "' data-slug='" + data.slug + "' data-category='" + data.category_id + "' data-image='" + data.featured_image + "' data-body='" + data.body + "'><span class='glyphicon glyphicon-edit'></span> Edit</button></td></tr>");
                    $('.edit-modal').css('display','none');
                    $('.posts-table').css('display','block');
                }

        });
    });

帖子的数据将显示在编辑表单中，但是当我尝试在编辑某些字段后提交它时，422 Unprocessable实体会一直显示。