Fix lookup error on invalid URLs

closes #119

src/servala/core/middleware.py

@@ -20,6 +20,10 @@ class OrganizationMiddleware:
         organization_slug = url.kwargs.get("organization")
         if organization_slug:
             pk = organization_slug.rsplit("-", maxsplit=1)[-1]
+            try:
+                pk = int(pk)
+            except ValueError:
+                pk = -1
             request.organization = get_object_or_404(Organization, pk=pk)
             with scope(organization=request.organization):
                 return self.get_response(request)