fix: event_start_trigger_in_event_node

Event Node should be ticked even without a start trigger in the scenario

engine/src/Node/EventNode.cpp

 /*******************************************************************************
  * Copyright (c) 2025 Ansys, Inc.
+ * Copyright (c) 2025 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License 2.0 which is available at
@@ -37,7 +38,7 @@ yase::NodeStatus EventNode::tick()
 
   auto current_status = TriggerableCompositeNode::tick();
 
-  if (start_trigger_->status() == yase::NodeStatus::kSuccess)
+  if (start_trigger_ == nullptr || start_trigger_->status() == yase::NodeStatus::kSuccess)
   {
     event_prioritizer_->EventStarted(name());
   }