getTransientActions should defend against null members even when assertions are disabled.

Cf.: https://github.com/jenkinsci/remote-terminal-access-plugin/commit/db24e2126b649689652ac8ddb100f3ef6680a422

core/src/main/java/hudson/model/Run.java

@@ -359,8 +359,13 @@ public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,Run
     public List<Action> getTransientActions() {
         List<Action> actions = new ArrayList<Action>();
         for (TransientBuildActionFactory factory: TransientBuildActionFactory.all()) {
-            actions.addAll(factory.createFor(this));
-            assert !actions.contains(null) : "null action added by " + factory;
+            for (Action created : factory.createFor(this)) {
+                if (created == null) {
+                    LOGGER.log(WARNING, "null action added by {0}", factory);
+                    continue;
+                }
+                actions.add(created);
+            }
         }
         return Collections.unmodifiableList(actions);
     }