Attempt to fix crash on exit

The update check runs on the thread pool and captures a raw pointer to the
KICAD_MANAGER_FRAME for CallAfter. If the update check completes during
frame destruction, the CallAfter targets a partially-destroyed window,
causing a segfault in wxWindowBase::RemoveEventHandler via wxAuiNotebook
destruction.  At least, that is the theory...

Fixes https://gitlab.com/kicad/code/kicad/-/issues/22593

(cherry picked from commit c0230e74c1)

kicad/kicad_manager_frame.cpp

@@ -314,6 +314,11 @@ KICAD_MANAGER_FRAME::~KICAD_MANAGER_FRAME()
     if( m_pcm )
         m_pcm->StopBackgroundUpdate();
 
+    // Stop update manager before tearing down the AUI framework. The update
+    // task runs on the thread pool and may call CallAfter on this frame, so it
+    // must complete before we uninitialize AUI or destroy child windows.
+    m_updateManager.reset();
+
     delete m_actions;
     delete m_toolManager;
     delete m_toolDispatcher;
@@ -378,6 +383,9 @@ void KICAD_MANAGER_FRAME::CreatePCM()
     m_pcm = std::make_shared<PLUGIN_CONTENT_MANAGER>(
             [this]( int aUpdateCount )
             {
+                if( Pgm().m_Quitting )
+                    return;
+
                 m_pcmUpdateCount = aUpdateCount;
 
                 if( aUpdateCount > 0 )

kicad/update_manager.cpp

@@ -229,7 +229,7 @@ void UPDATE_MANAGER::CheckForUpdate( wxWindow* aNoticeParent )
 
         // Check that the response is 200 (content provided)
         // We can also return 204 for no update
-        if( responseCode == 200 )
+        if( responseCode == 200 && !Pgm().m_Quitting )
         {
             nlohmann::json  update_json;
             UPDATE_RESPONSE response;
@@ -239,11 +239,14 @@ void UPDATE_MANAGER::CheckForUpdate( wxWindow* aNoticeParent )
                 update_json_stream >> update_json;
                 response = update_json.get<UPDATE_RESPONSE>();
 
-                if( response.version != settings->m_lastReceivedUpdate )
+                if( response.version != settings->m_lastReceivedUpdate && !Pgm().m_Quitting )
                 {
                     aNoticeParent->CallAfter(
                             [aNoticeParent, response]()
                             {
+                                if( Pgm().m_Quitting )
+                                    return;
+
                                 auto notice = new DIALOG_UPDATE_NOTICE( aNoticeParent,
                                                                         response.version,
                                                                         response.details_url,