Uncaught TypeError: Cannot read property 'style' of null

<input type="hidden" class="" name="id_sujet" value="<?php echo $suj['id_sujet']; ?>"> 
<input type="text" class="coment" name="texte_com" value="" placeholder="Votre commentaire..."> 
<a class="btn_input"><i class="far fa-image "></i><span class="name">Photos</span></a>
<input type="file" class="imgCom" id="imgFile_<?php echo $suj['id_sujet'];?>" name="img[]" lang="fr" accept=".jpg,.jpeg,.gif,.png" onchange="loadFileCom(event,<?php echo $suj['id_sujet'];?>)">
<div class="img_com" id="divCom_<?php echo $suj['id_sujet'];?>'"> 
        <img src="" id="outputCom_<?php echo $suj['id_sujet'];?>" class="img-fluid img-min" alt="">
        <a class="btn_del" onclick="delFileCom(event,'<?php echo $suj['id_sujet'];?>')"><i class="fas fa-trash-alt del" id="trash_<?php echo $suj['id_sujet'];?>"></i></a>
 </div>

var loadFileCom = function(event,idImg) {
  var reader = new FileReader();
  reader.onload = function() {
    event.target // l'élément input
      .nextElementSibling // l'élément div
      .children[0] // le 1er enfant du div, soit l'img
      .src = this.result;
    };
  reader.readAsDataURL(event.target.files[0]);
  var trash = document.getElementById('trash_'+idImg);
  trash.style.display = 'block';
  var divCom = document.getElementById('divCom_'+idImg);
  divCom.style.display = 'block';
};

var delFileCom = function(event,idImg) {
  var outputCom = document.getElementById('outputCom_'+idImg);
  outputCom.src = '';
  var trash = document.getElementById('trash_'+idImg);
  trash.style.display = 'none';
  imgFile = document.getElementById('imgFile_'+idImg);
  imgFile.value = "";
  var divCom = document.getElementById('divCom_'+idImg);
  divCom.style.display = 'none';
};

divCom.style.display = 'block';
divCom.style.display = 'none';