fixed playback/export flickering and hanging

project/clip.cpp

@@ -11,8 +11,6 @@
 #include "panels/timeline.h"
 #include "undo.h"
 
-#include <QDebug>
-
 extern "C" {
 	#include <libavformat/avformat.h>
 }

project/sequence.cpp

@@ -3,8 +3,6 @@
 #include "project/clip.h"
 #include "effects/transition.h"
 
-#include <QDebug>
-
 Sequence::Sequence() :
 	playhead(0),
     using_workarea(false),

project/undo.cpp

@@ -1,6 +1,5 @@
 #include "undo.h"
 
-#include <QDebug>
 #include <QTreeWidgetItem>
 #include <QMessageBox>
 #include <QCheckBox>