Как разделить список ul, если он не пуст

var completeSVG =
  '<svg version = "1.1" id = "Capa_1" xmlns = "http://www.w3.org/2000/svg" xmlns:xlink = "http://www.w3.org/1999/xlink" x = "0px" y = "0px" viewBox = "0 0 52 52" style = "enable-background:new 0 0 52 52;" xml:space = "preserve"> <g> <path d = "M38.252,15.336l-15.369,17.29l-9.259-7.407c-0.43-0.345-1.061-0.274-1.405,0.156c-0.345,0.432-0.275,1.061,0.156,1.406 l10,8C22.559,34.928,22.78,35,23,35c0.276,0,0.551-0.114,0.748-0.336l16-18c0.367-0.412,0.33-1.045-0.083-1.411 C39.251,14.885,38.62,14.922,38.252,15.336z"/> </svg>';
var removeSVG =
  '<svg version = "1.1" id = "Capa_1" id = "removeB" class = "removeB" xmlns = "http://www.w3.org/2000/svg" xmlns:xlink = "http://www.w3.org/1999/xlink" x = "0px" y = "0px" viewBox = "0 0 328.51 328.51" style = "enable-background:new 0 0 328.51 328.51;" xml:space = "preserve"> <polygon points = "229.044,88.858 164.255,153.647 99.466,88.858 88.858,99.466 153.647,164.255 88.858,229.044 99.466,239.651 164.255,174.862 229.044,239.651 239.651,229.044 174.862,164.255 239.651,99.466 		"/> </svg>';

 /*var button = document.querySelector(".complete");
button.addEventListener("click", function(){
        this.classList.toggle("clicked");
    });*/

function removeItem() {
  var item = this.parentNode.parentNode.parentNode;
  item.removeChild(this.parentNode.parentNode);
}

function completeItem() {
  var completeitem = this.parentNode.parentNode;
  var completeparent = completeitem.parentNode;

  var id = completeparent.id;

  var target = (id === "to-do")
    ? document.getElementById("completed")
    : document.getElementById("to-do");

  completeparent.removeChild(completeitem);
  target.prepend(completeitem);
}

document.getElementById("button-plus").addEventListener("click", function() {
  var value = document.getElementById("input").value;
  if (value) {
    addItem(value);
    document.getElementById("input").value = "";
  }
});
function addItem(text) {
  var list = document.getElementById("to-do");

  item = document.createElement("li");
  item.innerText = text;
  var buttons = document.createElement("div");
  buttons.classList.add("buttons");

  var remove = document.createElement("button");
  remove.classList.add("remove");
  remove.innerHTML = removeSVG;
  remove.addEventListener("click", removeItem);

  var complete = document.createElement("button");
  complete.classList.add("complete");
  complete.innerHTML = completeSVG;
  complete.addEventListener("click", completeItem);
  complete.addEventListener('click', function(){
    this.classList.toggle('clicked');
  });

  buttons.appendChild(remove);
  buttons.appendChild(complete);
  item.appendChild(buttons);

 
  
  list.prepend(item);
  
}

body {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
}

header {
  width: 100%;
  height: 70px;
  background: rgb(162, 193, 60);
  border-bottom-right-radius: 12px;
  border-bottom-left-radius: 12px;
  box-shadow: 0 0 5px rgb(159, 160, 155);
  padding: 0 10px 0 10px;
  box-sizing: border-box;
  display: flex;
  align-items: center;
}

header input {
 appearance: none;
 text-indent: 10px;
 border-bottom-right-radius: 25px;
 border-top-right-radius: 25px;
 border-top-left-radius: 12px;
 border-bottom-left-radius: 12px;
 width: 100%;
 background: rgb(233, 255, 170);
 height: 45px;
 font-family: Century Gothic;
 border: none;
 box-sizing: border-box;
 padding-right: 60px;
}

header button {
position: absolute;
right: 10px;
top: 13.5px;
height: 43px;
width: 50px;
border-bottom-right-radius: 25px;
border-top-right-radius: 25px;
appearance: none;
border: none;
background: rgb(238, 255, 173);
border-left: 2px solid rgb(162, 193, 60);
cursor: pointer;
}

button svg {
z-index: 6;
position: absolute;
border-bottom-right-radius: 25px;
border-top-right-radius: 25px;
right: 0;
top: -1px;
}/*
.container{
  width: 100%;
  margin: auto;
  border: 1px solid black;
}*/
 .to-do {
  width: 100%;
  float: left;
  list-style-type: none;
   box-sizing: border-box;
   padding: 0;
  /*border: 1px lid black;*/
}
.to-do li{
  width: 85%;
  background: rgb(233, 255, 170);
  min-height: 50px;
  margin: auto;
  border-radius: 5px;
  box-sizing: border-box;
  font-family: Century Gothic;
  padding: 0 105px 0 25px;
  position: relative;
  margin-top: 25px;
  display: flex;
  align-items: center;
  
}
.to-do li .buttons{
  position: absolute;
  top: 0;
  right: 0;
  height: 50px;
  width: 100px;
  background: white;
}
.to-do li .buttons button{
  appearance: none;
  width: 47.5px;
  height: 50px;
  box-sizing: border-box;
  position: relative;
  background: rgb(233, 255, 170);
  border: none;
  cursor: pointer;
}
.to-do li .buttons button:last-of-type:before{
  content: '';
  width: 0.8px;
  height: 29px;
  background: gray;
  opacity: 0.4;
  float: left;
  margin-left: -6px;
}/*
.to-do li button:nth-child(1):hover .x-fill{
  fill: red;
  transition-duration: 0.3s;
}
.to-do li button:nth-child(2):hover .tick-fill{
  fill: orange;
  transition-duration: 0.3s;
}*/
.complete svg{
  fill: gray;
}
.complete svg:hover{
  fill: green;
  opacity: 0.5;
}
.complete.clicked svg{
  fill: green;
  transition-duration: 0.3s;
}
.remove svg{
  fill: gray;
  opacity: 0.8;
}
.remove svg:hover{
  fill: red;
  opacity: 0.7;
  transition-duration: 0.3s;
}
ul.to-do#completed:not(:empty){
  position: relative;
}

ul.to-do#completed:not(:empty):before{
  content: '';
  width: 150px;
  height: 0.7px;
    background: black;
  position: absolute;
}

<head>

<title>To do List App</title>

</head>
<body>
<header>
  <input type = "text" placeholder = "Next on my to do list is....." id = "input">
  <button id = "button-plus">
 <svg width = "48" height = "43" xmlns = "http://www.w3.org/2000/svg" xmlns:svg = "http://www.w3.org/2000/svg">
  <rect fill = "#0186b2" height = "28" id = "svg_1" stroke = "#000000" stroke-opacity = "0" stroke-width = "5" width = "4" x = "19.5" y = "8.5"/>
  <rect fill = "#47bcbc" height = "3" id = "svg_2" stroke = "#000000" stroke-dasharray = "null" stroke-linecap = "null" stroke-linejoin = "null" stroke-opacity = "0" stroke-width = "5" width = "28" x = "7.5" y = "20.5"/>
</svg>
   
    </svg>
  </button>
</header>
  <div class = "container">
<ul id = "to-do" class = "to-do">
  </ul>
    <ul id = "completed" class = "to-do">
 </ul>
  </div>
  
</body>