diff --git a/Dockerfile b/Dockerfile
index fa77520..903342a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,7 +6,7 @@ RUN npm install && \
 
 FROM python:3.10.9-alpine
 
-ENV VERSION_NUMBER 0.2.1
+ENV VERSION_NUMBER 0.2.1-2-g734e6de
 ENV PROD 1
 
 RUN apk add \
diff --git a/pyproject.toml b/pyproject.toml
index 96a2dcc..06ec4ca 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -11,6 +11,8 @@ python = "^3.10"
 django = "^4.1.4"
 gunicorn = "^20.1.0"
 uvicorn = "^0.20.0"
+pandas = "^1.5.2"
+matplotlib = "^3.6.3"
 
 [tool.poetry.group.dev.dependencies]
 black = "^22.12.0"
diff --git a/src/web/tracker/templates/list_sessions.html b/src/web/tracker/templates/list_sessions.html
index 2a140a1..7f389d8 100644
--- a/src/web/tracker/templates/list_sessions.html
+++ b/src/web/tracker/templates/list_sessions.html
@@ -4,11 +4,13 @@
 
 {% block content %}
         <div class="text-center text-xl mb-4 dark:text-slate-400">
+            {% if dataset.count > 0 %}
             <a href="{% url 'start_session' dataset.last.purchase.id %}">
                 <button type="button" title="Track last tracked" class="py-1 px-2 bg-green-600 hover:bg-green-700 focus:ring-green-500 focus:ring-offset-blue-200 text-white transition ease-in duration-200 text-center text-base font-semibold shadow-md focus:outline-none focus:ring-2 focus:ring-offset-2 rounded-lg ">
                     New session of {{ dataset.last.purchase }}
                 </button>
             </a>
+            {% endif %}
             {% if purchase %}
             <h1>Listing sessions only for purchase "{{ purchase }}"</h1>
             <h2>Total playtime: {{ total_duration }} over {{ dataset.count }} sessions.</h2>