neutrino.h: add signal OnShutDown

was missed in context with similar OnBeforeRestart

src/neutrino.cpp

@@ -3984,6 +3984,8 @@ void CNeutrinoApp::ExitRun(int exit_code)
 		SDT_ReloadChannels();
 
 	dprintf(DEBUG_INFO, "exit\n");
+	OnShutDown();
+
 	StopSubtitles();
 	stopPlayBack();
 

src/neutrino.h

@@ -229,6 +229,7 @@ public:
 	bool adjustToChannelID(const t_channel_id channel_id);
 	//signal/event handler before restart of neutrino gui
 	sigc::signal<bool> OnBeforeRestart;
+	sigc::signal<void> OnShutDown;
 	sigc::signal<void> OnAfterSetupFonts;
 	void channelRezap();