Don't crash when rendering None price

app/app.py

@@ -19,7 +19,7 @@ from login import init_login
 from markupsafe import Markup
 from models import db
 from models.anonymous_user import AnonymouseUser
-from utils import euro_string, price_range_string
+from utils import euro_string, price_range_string, ignore_none
 from zeus import init_oauth
 
 
@@ -151,6 +151,7 @@ def add_template_filters(app: Flask) -> None:
     app.template_filter("price_range")(price_range_string)
     app.template_filter("any")(any)
     app.template_filter("all")(all)
+    app.template_filter("ignore_none")(ignore_none)
 
 
 def create_app():

app/templates/order.html

@@ -281,7 +281,7 @@
 								{{ "disabled" if not order.can_modify_payment(current_user.id) }}>
 
 						<span class="price" style="{{ 'opacity: 0.5' if paid }}">
-							{{ order_items | map(attribute="price") | sum | euro }}
+							{{ order_items | map(attribute="price") | ignore_none | sum | euro }}
 						</span>
 
 						{% if paid %}<span class="glyphicon glyphicon-ok" style="opacity: 0.5"></span>{% endif %}

app/utils.py

@@ -4,10 +4,12 @@ import re
 from typing import Iterable, Optional
 
 
-def euro_string(value: int, unit="€ ") -> str:
+def euro_string(value: Optional[int], unit="€ ") -> str:
     """
     Convert cents to string formatted euro
     """
+    if value is None:
+        return "✗"
     euro, cents = divmod(value, 100)
     if cents:
         return f"{unit}{euro}.{cents:02}"