Остановить удаление HTML5 из ​​перенаправления Firefox

var src  = document.querySelector('#src tbody'),
    dest = document.querySelector('#dest tbody');

var people = [
  {name:'Gavin', age:42},
  {name:'Bjørn', age:17},
  {name:'Leyla', age:24}
];

people.forEach(function(person,i){
  var tr = rowFor(person);
  src.appendChild(tr);

  tr.draggable = true;
  tr.addEventListener( 'dragstart', function(evt){
    this.classList.add('drag','selected');
    evt.dataTransfer.dropEffect = 'copy';
    evt.dataTransfer.setData( 'text', i );
    return false;
  }, false );

  tr.addEventListener( 'dragend', function(evt){
    if (evt.preventDefault) evt.preventDefault();
    this.classList.remove('drag');
    return false;
  }, false );
});

dest.addEventListener( 'dragenter', function(evt){
  this.classList.add('over');
  return false;
}, false );

dest.addEventListener( 'dragover', function(evt){
  evt.dataTransfer.dropEffect = 'copy';
  this.classList.add('over');
  if (evt.preventDefault) evt.preventDefault();
  return false;
}, false );

dest.addEventListener( 'dragleave', function(evt){
  this.classList.remove('over');
  return false;
}, false );

dest.addEventListener( 'drop', function(evt) {
  this.classList.remove('over');
  var index = evt.dataTransfer.getData('Text');
  var dup = rowFor( people[index] );
  dest.appendChild( dup );
  if (evt.stopPropagation) evt.stopPropagation();
  return false;
}, false );

function rowFor(obj){
  var tr = document.createElement('tr');
  tr.innerHTML = "<td>"+obj.name+"</td><td>"+obj.age+"</td>";
  return tr;
}

body { background:#eee }
#wrap {
  display:flex;
  flex-direction:row;
  justify-content:space-between;
  align-items:flex-start;
  flex-grow:1;
  height:400px;
  padding:1em
}
table { width:200px; border-collapse:collapse; border:1px solid #ccc }
tbody { background:#fff }
th,td { padding:0 5px }
th { text-align:left; background:#ddd }
caption { background:#ccc }

table.over { border:2px solid yellow }
tr.selected td { background:lightblue }

table { display:flex; flex-flow:column; height:100%; margin-right:4px; overflow:hidden }
table caption { flex:0 0 auto; width:100%; display:block }
table thead { flex:0 0 auto; width:calc(100% + 1px) }
table tbody { flex:1 1 auto; display:block; overflow-y:auto }
table tbody tr { width:100% }
table thead,
table tbody tr { display:table; table-layout:fixed }
tbody tr { cursor:default }
thead th:last-child,
tbody td:last-child { width:33%; }

<div id="wrap">

<table id="src">
  <caption>drag from here</caption>
  <thead><tr><th>name</th><th>age</th></tr></thead>
  <tbody></tbody>
</table>

<table id="dest">
  <caption>drag to here</caption>
  <thead><tr><th>name</th><th>age</th></tr></thead>
  <tbody></tbody>
</table>

</div>