Fix crash on exit from MIDI connections (#4340)

include/MidiPort.h

@@ -124,6 +124,8 @@ public:
 		return m_writablePorts;
 	}
 
+	void invalidateCilent();
+
 	MidiPortMenu* m_readablePortsMenu;
 	MidiPortMenu* m_writablePortsMenu;
 

src/core/midi/MidiClient.cpp

@@ -38,6 +38,10 @@ MidiClient::MidiClient()
 MidiClient::~MidiClient()
 {
 	//TODO: noteOffAll(); / clear all ports
+	for (MidiPort* port : m_midiPorts)
+	{
+		port->invalidateCilent();
+	}
 }
 
 

src/core/midi/MidiPort.cpp

@@ -27,9 +27,12 @@
 
 #include "MidiPort.h"
 #include "MidiClient.h"
+#include "MidiDummy.h"
 #include "Note.h"
 #include "Song.h"
 
+static MidiDummy s_dummyClient;
+
 
 
 MidiPort::MidiPort( const QString& name,
@@ -410,4 +413,7 @@ void MidiPort::updateOutputProgram()
 
 
 
-
+void MidiPort::invalidateCilent()
+{
+	m_midiClient = &s_dummyClient;
+}