Fix: Schedule SLA print uploads too (the same way as FFF)

src/slic3r/GUI/BackgroundSlicingProcess.hpp

@@ -167,6 +167,7 @@ private:
     bool                invalidate_all_steps();
     // If the background processing stop was requested, throw CanceledException.
     void                throw_if_canceled() const { if (m_print->canceled()) throw CanceledException(); }
+    void                prepare_upload();
 
 	// wxWidgets command ID to be sent to the platter to inform that the slicing is finished, and the G-code export will continue.
 	int 						m_event_slicing_completed_id 	= 0;