Update exclude filter for Tenant Subscriptions page

b/c in v4.0.0 the subscription format was update to include the
vendor prefix.

This change fixes a bug where the Tenant Subscription page cannot find
the last active purchase b/c it is filtering incorrectly.

Author: atodorov

tcms_github_marketplace/views.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2019-2024 Alexander Todorov <[email protected]>
+# Copyright (c) 2019-2025 Alexander Todorov <[email protected]>
 #
 # Licensed under GNU Affero General Public License v3 or later (AGPLv3+)
 # https://www.gnu.org/licenses/agpl-3.0.html
@@ -773,7 +773,7 @@ def get_object(self, queryset=None):
         which has the subscription field set! Note that some events,
         e.g. order.canceled may have this field set to None
         """
-        return self.get_queryset().exclude(subscription=None).first()
+        return self.get_queryset().exclude(subscription__contains="None").first()
 
     def get_context_data(self, **kwargs):
         context = super().get_context_data(**kwargs)