Fix failing test, when deployment platform is not bound to a cluster.

app/models/environment.rb

@@ -233,8 +233,10 @@ class Environment < ActiveRecord::Base
   end
 
   def cluster_prometheus_adapter
-    cluster = project.deployment_platform&.cluster
-    return unless cluster&.application_prometheus&.installed?
+    return unless project.deployment_platform.respond_to?(:cluster)
+
+    cluster = project.deployment_platform.cluster
+    return unless cluster.application_prometheus&.installed?
 
     cluster.application_prometheus
   end