Jquery ui-sortable - unable to drop tr in empty tbody

Here's how I solved the issue with being unable to drop a tr in an empty tbody:

$(function() {

    var sort1 = $('#sort1 tbody');
    var sort2 = $('#sort2 tbody');

   sizeCheck(sort1);
   sizeCheck(sort2);

   //Start the jQuery Sortable for Active and Fresh Promo Tables
   $("#sort1 tbody, #sort2 tbody").sortable({

     items: ">*:not(.sort-disabled)",

     deactivate: function(e, ui) {

        sizeCheck(sort1);
        sizeCheck(sort2);

     },
     //Connect tables to pass data
     connectWith: ".contentTable tbody"

   }).disableSelection();

});

//Prevent empty tbody from not allowing items dragged into it

function sizeCheck(item){
    if($(item).height() == 0){
        $(item).append('<tr class="sort-disabled"><td></td></tr>');
    }
}

In my case it was about table and tbody collapsing to size 0x0 when no items present. What worked was providing some minimal size for the table and tbody, like this:

table.items-table {
    width: 100%; /*needed for dropping on empty table to work - can be any non-zero value*/
}

table.items-table >tbody { /*needed for dropping on empty table to work */
    display: block;
    min-height: 10px;
}

That was all that was needed.

Based on Ismael Miguel comment on Cetnar answer, here is my working solution.

• I send different ajax call for each table (urgent, normal, low priority tasks), and it works fine with empty table dropping.
• In database I update all tasks present in the array sent by ajax with a sorting column.

jQuery code :

$('.draggable-zone').sortable({
    items:       'tr.draggable',
    helper:      'clone',
    appendTo:    'body',
    connectWith: '.draggable-zone',
    update: function(e, ui) {
        $.ajax({
            url:  '/inve/new/sort', 
            type: 'POST',
            data: $(this).sortable('serialize', { 
                key: $(this).attr('data-partl')
            })
        });
    },
    receive: function(e, ui) {
        var $parent = ui.item.parent(); 
        if($parent.is('table')){
            $parent.find('tbody').append(ui.item);
        }
    }
});

HTML / Smarty template (1 table only) :

<table class="table table-striped table-hover table-bordered draggable-zone" data-partl="normal[]">
    <tbody>
        {foreach $data.normal as $task}
            <tr class="draggable" id="sort_{$task.id}">
                <td><b>{$task.title}</b></td>
                ...
            </tr>
        {/foreach}
    </body>
</table>
...