Tree view doesn't work in some installations

app/views/dmsf/dmsf_rows.js.erb

@@ -1,7 +1,12 @@
 // Store DMSF controls
-var dmsfButtons = $('#dmsf_buttons')[0].outerHTML
-var dmsfTag = $('#dmsf_tag')[0].outerHTML
+var dmsfButtons = $('#dmsf_buttons')[0].outerHTML;
 var browserInfo = $('#browser_info').text();
+var dmsfTag;
+
+if(($('#dmsf_tag') != null) && $('#dmsf_tag')[0] != null) {
+
+    dmsfTag = $('#dmsf_tag')[0].outerHTML
+}
 
 // Destroy the original dataTable
 $("#browser").dataTable().fnDestroy();
@@ -28,7 +33,11 @@ $('#browser').dataTable({
   ],
   'fnInitComplete': function() {
     $(dmsfButtons).prependTo($('#browser_wrapper div.fg-toolbar')[0]);
+
+    if($(dmsfTag) != null) {
+
         $(dmsfTag).prependTo($('#browser_wrapper div.fg-toolbar')[0]);
+    }
   },
   'fnInfoCallback': function( oSettings, iStart, iEnd, iMax, iTotal, sPre ) {
     return browserInfo;

assets/javascripts/redmine_dmsf.js

@@ -138,13 +138,19 @@ function dmsfExpandRows(EL, parentRow, url) {
 
   var pos = $(parentRow).find('#dmsf_position').text();
 
-  return $.ajax({
+  $.ajax({
     url: url,
     type: 'post',
+    dataType: 'html',
     data: {
       folder_id: EL,
       row_id: parentRow.id,
       idnt: idnt,
       pos: pos}
+  }).done(function(data) {
+      eval(data);
+  })
+  .fail(function() {
+      alert('An error in rows expanding');
   });
 }