Fix Position Line gradient appearing in all editors no matter which one is playing (#7882)

include/PositionLine.h

@@ -28,6 +28,8 @@
 
 #include <QWidget>
 
+#include "Song.h"
+
 namespace lmms::gui
 {
 
@@ -37,7 +39,7 @@ class PositionLine : public QWidget
 	Q_PROPERTY(bool tailGradient MEMBER m_hasTailGradient)
 	Q_PROPERTY(QColor lineColor MEMBER m_lineColor)
 public:
-	PositionLine(QWidget* parent);
+	PositionLine(QWidget* parent, Song::PlayMode playMode);
 
 public slots:
 	void zoomChange(float zoom);
@@ -45,6 +47,8 @@ public slots:
 private:
 	void paintEvent(QPaintEvent* pe) override;
 
+	Song::PlayMode m_playMode;
+
 	bool m_hasTailGradient;
 	QColor m_lineColor;
 };