FIX: use thread stack to keep shared ref of PrinterFileSystem

Change-Id: I86dce263f43eb65074d4fec777cb08885505b7cf
(cherry picked from commit 1dbc32b2335c33831ac94a787c8e7ec7d898ccba)

src/slic3r/GUI/Monitor.cpp

@@ -227,11 +227,6 @@ void MonitorPanel::set_default()
     /* reset side tool*/
     //m_bitmap_wifi_signal->SetBitmap(wxNullBitmap);
 
-#if !BBL_RELEASE_TO_PUBLIC
-    /* reset time lapse panel */
-    m_media_file_panel->SetMachineObject(nullptr);
-#endif
-
     wxGetApp().sidebar().load_ams_list({});
 }