Fixing crash creating new level when simulate mode is on

Signed-off-by: Mikhail Naumov <mnaumov@amazon.com>

Code/Editor/CryEdit.cpp

@@ -57,6 +57,7 @@ AZ_POP_DISABLE_WARNING
 #include <AzFramework/StringFunc/StringFunc.h>
 #include <AzFramework/Terrain/TerrainDataRequestBus.h>
 #include <AzFramework/ProjectManager/ProjectManager.h>
+#include <AzFramework/Spawnable/RootSpawnableInterface.h>
 
 // AzToolsFramework
 #include <AzToolsFramework/Component/EditorComponentAPIBus.h>
@@ -3019,6 +3020,15 @@ CCryEditApp::ECreateLevelResult CCryEditApp::CreateLevel(const QString& levelNam
         bool bIsDocModified = GetIEditor()->GetDocument()->IsModified();
         OnSwitchPhysics();
         GetIEditor()->GetDocument()->SetModifiedFlag(bIsDocModified);
+
+        if (usePrefabSystemForLevels)
+        {
+            auto* rootSpawnableInterface = AzFramework::RootSpawnableInterface::Get();
+            if (rootSpawnableInterface)
+            {
+                rootSpawnableInterface->ProcessSpawnableQueue();
+            }
+        }
     }
 
     const QScopedValueRollback<bool> rollback(m_creatingNewLevel);

Code/Framework/AzFramework/AzFramework/Spawnable/RootSpawnableInterface.h

@@ -61,6 +61,10 @@ namespace AzFramework
         //! be deleted and the spawnable asset to be released. This call is automatically done when
         //! AssignRootSpawnable is called while a root spawnable is assigned.
         virtual void ReleaseRootSpawnable() = 0;
+        //! Force processing all SpawnableEntitiesManager requests immediately
+        //! This is useful when loading a different level while SpawnableEntitiesManager still has
+        //! pending requests
+        virtual void ProcessSpawnableQueue() = 0;
     };
 
     using RootSpawnableInterface = AZ::Interface<RootSpawnableDefinition>;

Code/Framework/AzFramework/AzFramework/Spawnable/SpawnableSystemComponent.cpp

@@ -45,8 +45,7 @@ namespace AzFramework
 
     void SpawnableSystemComponent::OnTick(float /*deltaTime*/, AZ::ScriptTimePoint /*time*/)
     {
-        m_entitiesManager.ProcessQueue(
-            SpawnableEntitiesManager::CommandQueuePriority::High | SpawnableEntitiesManager::CommandQueuePriority::Regular);
+        ProcessSpawnableQueue();
         RootSpawnableNotificationBus::ExecuteQueuedEvents();
     }
 
@@ -121,6 +120,12 @@ namespace AzFramework
         m_rootSpawnableId = AZ::Data::AssetId();
     }
 
+    void SpawnableSystemComponent::ProcessSpawnableQueue()
+    {
+        m_entitiesManager.ProcessQueue(
+            SpawnableEntitiesManager::CommandQueuePriority::High | SpawnableEntitiesManager::CommandQueuePriority::Regular);
+    }
+
     void SpawnableSystemComponent::OnRootSpawnableAssigned([[maybe_unused]] AZ::Data::Asset<Spawnable> rootSpawnable,
         [[maybe_unused]] uint32_t generation)
     {

Code/Framework/AzFramework/AzFramework/Spawnable/SpawnableSystemComponent.h

@@ -75,6 +75,7 @@ namespace AzFramework
 
         uint64_t AssignRootSpawnable(AZ::Data::Asset<Spawnable> rootSpawnable) override;
         void ReleaseRootSpawnable() override;
+        void ProcessSpawnableQueue() override;
 
         //
         // RootSpawnbleNotificationBus