diff --git a/django/website/hid/views.py b/django/website/hid/views.py
index e7cfd2c6c17b136134be290d4b41d701e84b4120..154605ee90e822ce78fe5f0bcdf1ea9924e29af2 100644
--- a/django/website/hid/views.py
+++ b/django/website/hid/views.py
@@ -226,7 +226,7 @@ def process_items(request):
         action = request.POST.get('action')
         if action == DELETE_COMMAND:
             delete_items(request, selected)
-        elif action.startswith(ADD_CATEGORY_PREFIX):
+        elif action and action.startswith(ADD_CATEGORY_PREFIX):
             category = action[len(ADD_CATEGORY_PREFIX):]
             add_items_categories(request, selected, category)
         else: