diff --git a/swh/web/templates/includes/vault-ui.html b/swh/web/templates/includes/vault-ui.html
index 6a2bd15b..f60596df 100644
--- a/swh/web/templates/includes/vault-ui.html
+++ b/swh/web/templates/includes/vault-ui.html
@@ -1,211 +1,211 @@
 {% load static %}
 
 <div class="panel panel-default" style="overflow-x: auto;">
   <div class="panel-heading">
       <h2>Download content from the Software Heritage Vault</h2>
   </div>
   <div class="panel-body">
     <p>
       This interface enables to track the status of the different Software Heritage
       Vault cooking tasks created while browsing the archive.
     </p>
     <p>
       Once a cooking task is finished, a link will be made available in order to
       download the associated archive.
     </p>
     <button type="button" class="btn btn-md btn-swh" id="vault-remove-tasks">Remove selected tasks</button>
     <div class="table-responsive">
       <table class="table swh-vault-table" id="vault-cooking-tasks">
         <thead>
           <tr>
             <th><input type="checkbox" id="vault-tasks-toggle-selection"/></th>
             <th style="width: 100px">Object type</th>
             <th>Object id</th>
             <th style="width: 350px">Cooking status</th>
             <th style="width: 320px"></th>
           </tr>
         </thead>
         <tbody></tbody>
       </table>
     </div>
   </div>
 </div>
 
 <script>
   var cook_dir_url = "{% url 'vault-cook-directory' 'ffff' %}";
   var cook_rev_url = "{% url 'vault-cook-revision_gitfast' 'ffff' %}";
   var browse_dir_url = "{% url 'browse-directory' 'ffff' %}";
   var browse_rev_url = "{% url 'browse-revision' 'ffff' %}";
 
   var progress = '<div class="progress" style="margin-bottom: 0px;"> \
                     <div class="progress-bar progress-bar-success progress-bar-striped" \
                          role="progressbar" aria-valuenow="100" aria-valuemin="0" \
                          aria-valuemax="100" style="width: 100%;height: 100%;"> \
                     </div> \
                   </div>';
 
   function update_progress_bar(progress_bar, cooking_task) {
     if (cooking_task.status == 'new') {
       progress_bar.css('background-color', 'rgba(128, 128, 128, 0.5)');
     } else if (cooking_task.status == 'pending') {
       progress_bar.css('background-color', 'rgba(0, 0, 255, 0.5)');
     } else if (cooking_task.status == 'done') {
       progress_bar.css('background-color', 'rgba(0, 255, 0, 0.5)');
     } else if (cooking_task.status == 'failed') {
       progress_bar.css('background-color', 'rgba(255, 0, 0, 0.5)');
       progress_bar.css('background-image', 'none');
     }
     progress_bar.text(cooking_task.progress_message || cooking_task.status);
     if (cooking_task.status == 'new' || cooking_task.status == 'pending') {
       progress_bar.addClass('active');
     } else {
       progress_bar.removeClass('progress-bar-striped');
     }
   }
 
   function check_vault_cooking_tasks() {
     var vault_cooking_tasks = JSON.parse(localStorage.getItem("swh-vault-cooking-tasks"));
-    if (vault_cooking_tasks.length == 0) {
+    if (!vault_cooking_tasks || vault_cooking_tasks.length == 0) {
       $('.swh-vault-table tbody tr').remove();
       check_vault_id = setTimeout(check_vault_cooking_tasks, polling_interval);
       return;
     }
     var cooking_urls = [];
     var tasks = {};
     var current_object_ids = [];
     for (var i = 0 ; i < vault_cooking_tasks.length ; ++i) {
       var cooking_task = vault_cooking_tasks[i];
       current_object_ids.push(cooking_task.object_id);
       tasks[cooking_task.object_id] = cooking_task;
       var cooking_url;
       if (cooking_task.object_type == 'directory') {
         cooking_url = cook_dir_url.replace('ffff', cooking_task.object_id);
       } else {
         cooking_url = cook_rev_url.replace('ffff', cooking_task.object_id);
       }
       if (cooking_task.status != 'done' && cooking_task.status != 'failed') {
         cooking_urls.push($.ajax(cooking_url));
       }
     }
     $('.swh-vault-table tbody tr').each(function(i, row) {
       var object_id = $(row).find('.vault-object-id').data('object-id');
       if ($.inArray(object_id, current_object_ids) == -1) {
         $(row).remove();
       }
     });
     $.when.apply($, cooking_urls).then(function() {
       var table = $("#vault-cooking-tasks tbody");
       for (var i = 0 ; i < cooking_urls.length ; ++i) {
         var resp;
         if (cooking_urls.length == 1) {
           resp = arguments[i];
         } else {
           resp = arguments[i][0];
         }
         var cooking_task = tasks[resp.obj_id];
         cooking_task.status = resp.status;
         cooking_task.fetch_url = resp.fetch_url;
         cooking_task.progress_message = resp.progress_message;
       }
       for (var i = 0 ; i < vault_cooking_tasks.length ; ++i) {
         var cooking_task = vault_cooking_tasks[i];
 
         var row_task = $('#vault-task-' + cooking_task.object_id);
 
         if (!row_task.length) {
 
           var browse_url;
           if (cooking_task.object_type == 'directory') {
             browse_url = browse_dir_url.replace('ffff', cooking_task.object_id);
           } else {
             browse_url = browse_rev_url.replace('ffff', cooking_task.object_id);
           }
 
           var progress_bar = $.parseHTML(progress)[0];
           var progress_bar_content = $(progress_bar).find('.progress-bar');
           update_progress_bar(progress_bar_content, cooking_task);
           var table_row;
           if (cooking_task.object_type == 'directory') {
             table_row = '<tr id="vault-task-' + cooking_task.object_id + '" title="Once downloaded, the directory can be extracted with the ' +
                         'following command:\n\n$ tar xvzf ' + cooking_task.object_id + '.tar.gz">';
           } else {
             table_row = '<tr id="vault-task-' + cooking_task.object_id + '"  title="Once downloaded, the git repository can be imported with the ' +
                         'following commands:\n\n$ git init\n$ zcat ' + cooking_task.object_id + '.gitfast.gz | git fast-import">';
           }
           table_row += '<td><input type="checkbox" class="vault-task-toggle-selection"/></td>';
           if (cooking_task.object_type == 'directory') {
             table_row += '<td><i class="fa fa-folder fa-fw" aria-hidden="true"></i>directory</td>';
           } else {
             table_row += '<td><i class="octicon octicon-git-commit fa-fw"></i>revision</td>';
           }
           table_row += '<td class="vault-object-id" data-object-id="' + cooking_task.object_id + '"><a href="' + browse_url + '">' + cooking_task.object_id + '</a></td>';
           table_row += '<td style="width: 350px">' + progress_bar.outerHTML + '</td>';
           var dl_link = 'Waiting for download link to be available';
           if (cooking_task.status == 'done') {
             dl_link = '<a class="btn btn-md btn-swh" href="' + cooking_task.fetch_url +
                       '"><i class="fa fa-download fa-fw" aria-hidden="true"></i>Download</a>';
           } else if (cooking_task.status == 'failed') {
             dl_link = '';
           }
           table_row += '<td class="vault-dl-link" style="width: 320px">' + dl_link + '</td>';
           table_row += '</tr>';
           table.prepend(table_row);
         } else {
           var progress_bar = row_task.find('.progress-bar');
           update_progress_bar(progress_bar, cooking_task);
           var dl_link = row_task.find('.vault-dl-link');
           var dl_link = row_task.find('.vault-dl-link');
           if (cooking_task.status == 'done') {
             dl_link[0].innerHTML = '<a class="btn btn-md btn-swh" href="' + cooking_task.fetch_url +
                                    '"><i class="fa fa-download fa-fw" aria-hidden="true"></i>Download</a>';
           } else if (cooking_task.status == 'failed') {
             dl_link[0].innerHTML = '';
           }
         }
       }
       localStorage.setItem("swh-vault-cooking-tasks", JSON.stringify(vault_cooking_tasks));
       check_vault_id = setTimeout(check_vault_cooking_tasks, polling_interval);
     });
   }
 
   $('#vault-tasks-toggle-selection').change(function() {
     $('.vault-task-toggle-selection').prop('checked', this.checked);
   });
 
   $('#vault-remove-tasks').click(function() {
     clearTimeout(check_vault_id);
     var tasks_to_remove = [];
     $('.swh-vault-table tbody tr').each(function(i, row) {
       var task_selected = $(row).find('.vault-task-toggle-selection').prop('checked');
       if (task_selected) {
         var object_id = $(row).find('.vault-object-id').data('object-id');
         tasks_to_remove.push(object_id);
         $(row).remove();
       }
     });
     var vault_cooking_tasks = JSON.parse(localStorage.getItem("swh-vault-cooking-tasks"));
     vault_cooking_tasks = jQuery.grep(vault_cooking_tasks, function(task) {
       return $.inArray(task.object_id, tasks_to_remove) == -1;
     });
     localStorage.setItem("swh-vault-cooking-tasks", JSON.stringify(vault_cooking_tasks));
     $('#vault-tasks-toggle-selection').prop('checked', false);
     check_vault_id = setTimeout(check_vault_cooking_tasks, polling_interval);
   });
 
   var polling_interval = 5000;
 
   var check_vault_id = setTimeout(check_vault_cooking_tasks, polling_interval);
 
   $(document).on('shown.bs.tab', 'a[data-toggle="tab"]', function (e) {
     if (e.target.text == 'Vault') {
       clearTimeout(check_vault_id);
       check_vault_cooking_tasks();
     }
   });
 
   window.onfocus = function() {
     clearTimeout(check_vault_id);
     check_vault_cooking_tasks();
   };
 
 </script>
\ No newline at end of file