Viewport: fix to allow multiple shutdown / calls to DestroyPlatformWindows(). (#2769)
diff --git a/imgui.cpp b/imgui.cpp
index 70914d2..5048bc5 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -11173,7 +11173,11 @@
         if (g.PlatformIO.Platform_DestroyWindow)
             g.PlatformIO.Platform_DestroyWindow(viewport);
         IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL);
-        viewport->PlatformWindowCreated = false;
+
+        // Don't clear PlatformWindowCreated for the main viewport, as we initially set that up to true in Initialize()
+        // The right-er way may be to leave it to the back-end to set this flag all-together, and made the flag public.
+        if (viewport->ID != IMGUI_VIEWPORT_DEFAULT_ID)
+            viewport->PlatformWindowCreated = false;
     }
     else
     {