fix: handle missing family history template

mysite/familytree/templates/familytree/history.html

@@ -10,11 +10,19 @@ <h2>Family history: </h2>
         {% if profile.connection_notes %}
                 <p>{{ profile.connection_notes }}</p>
         {%  endif %}
-    {% for branch in accessible_branches %}
-        {% get_history_filepath branch as filepath %}
-        <div class="circled_section">
-                {% include filepath %}
-        </div>
-    {% endfor %}
 
+        {% for branch in accessible_branches %}
+            {% get_history_filepath branch as filepath %}
+            {% template_exists filepath as result %}
+
+                <div class="circled_section">
+                    {% if result %}
+                        {% include filepath %}
+                    {% else %}
+                        {{branch}} history still to be written <br/>
+                        Add it here: {{filepath}}
+                    {% endif %}
+                </div>
+
+        {% endfor %}
 {% endblock content %}

mysite/familytree/templatetags/familytree_extras.py

@@ -1,8 +1,19 @@
 from django import template
+from django.template.defaultfilters import stringfilter
 from django.utils.timesince import timesince
 
 register = template.Library()
 
+# @register.filter
+# @stringfilter
+@register.simple_tag
+def template_exists(value):
+    try:
+        template.loader.get_template(value)
+        return True
+    except template.TemplateDoesNotExist:
+        return False
+
 
 @register.simple_tag
 def generation_class(generation_int):