Audio/MidiJack: Fix invalid read: (2) of #5408

This patch
* makes `m_stopped` atomic
* initializes `m_stopped` correctly to `true`
* moves the initialization of `m_stopped` to the point where jack ports
  are already connected

include/AudioJack.h

@@ -34,6 +34,7 @@
 #include "AudioWeakJack.h"
 #endif
 
+#include <atomic>
 #include <QtCore/QVector>
 #include <QtCore/QList>
 #include <QtCore/QMap>
@@ -106,7 +107,7 @@ private:
 	jack_client_t * m_client;
 
 	bool m_active;
-	bool m_stopped;
+	std::atomic<bool> m_stopped;
 
 	MidiJack *m_midiClient;
 	QVector<jack_port_t *> m_outputPorts;

src/core/audio/AudioJack.cpp

@@ -56,6 +56,8 @@ AudioJack::AudioJack( bool & _success_ful, Mixer*  _mixer ) :
 	m_framesDoneInCurBuf( 0 ),
 	m_framesToDoInCurBuf( 0 )
 {
+	m_stopped = true;
+
 	_success_ful = initJackClient();
 	if( _success_ful )
 	{
@@ -201,8 +203,6 @@ bool AudioJack::initJackClient()
 
 void AudioJack::startProcessing()
 {
-	m_stopped = false;
-
 	if( m_active || m_client == NULL )
 	{
 		return;
@@ -245,6 +245,7 @@ void AudioJack::startProcessing()
 		}
 	}
 
+	m_stopped = false;
 	free( ports );
 }