* Fix return from assembly linux
* Tie deferred callback to canvas lifetime and add shutdown guards
Use m_canvas->CallAfter instead of wxGetApp().CallAfter to ensure the callback is only executed if the canvas is still alive.
Add early returns if wxGetApp().is_closing() is true before accessing plater or the 3D canvas, reducing the risk of use-after-free during application shutdown.
Addresses feedback regarding potential UI teardown race conditions.
* copilot suggestion
* Use local reference to wxGetApp() in Return button callback
Replace multiple calls to wxGetApp() with a single local reference
to improve readability and avoid redundant function calls.
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