fixing crash when opening different level during simulation mode (#6762)

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

Code/Editor/CryEdit.cpp

@@ -3363,6 +3363,10 @@ CCryEditDoc* CCryEditApp::OpenDocumentFile(const char* filename, bool addToMostR
         return GetIEditor()->GetDocument();
     }
 
+    bool usePrefabSystemForLevels = false;
+    AzFramework::ApplicationRequests::Bus::BroadcastResult(
+        usePrefabSystemForLevels, &AzFramework::ApplicationRequests::IsPrefabSystemForLevelsEnabled);
+
     // If we are loading and we're in simulate mode, then switch it off before we do anything else
     if (GetIEditor()->GetGameEngine() && GetIEditor()->GetGameEngine()->GetSimulationMode())
     {
@@ -3370,6 +3374,15 @@ CCryEditDoc* CCryEditApp::OpenDocumentFile(const char* filename, bool addToMostR
         bool bIsDocModified = GetIEditor()->GetDocument()->IsModified();
         OnSwitchPhysics();
         GetIEditor()->GetDocument()->SetModifiedFlag(bIsDocModified);
+
+        if (usePrefabSystemForLevels)
+        {
+            auto* rootSpawnableInterface = AzFramework::RootSpawnableInterface::Get();
+            if (rootSpawnableInterface)
+            {
+                rootSpawnableInterface->ProcessSpawnableQueue();
+            }
+        }
     }
 
     // We're about to start loading a level, so start recording errors to display at the end.